GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
ELECTRONICS CIRCUIT AND APPLICATION
(3321101)
LAB MANUAL
EC DEPARTMENT
GOVERNMENT POLYTECHNIC
GANDHINAGAR
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
LIST OF EXPERIMENTS
SR.
NO
1
2
3
4
5
6
7
8
9
10
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12
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15
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EXPERIMENT
To study multimeter for measuring electrical parameters
Determine voltage and frequency of various waves using
CRO.
To study clıppıng crcuıts and observe input-output
waveforms.
To study clamping circuits and observe input-output
waveforms.
Obtain the V-I characteristics of zener diode.
To study zener diode as a voltage regulator.
To study V-I Characteristics of Photo diode.
To study LDR.
Display number using seven segment display
To study input and output characteristics of CB
amplifier circuit.
To study input and output characteristics of CE
amplifier circuit.
To study voltage divider bias analysis, load line and Q
point.
To study single stage transistor amplifier frequency
response.
To study two stages RC coupled amplifier frequency
response.
To study Transistor as a switch, as a base-biased LED
driver.
To study Transistor as a switch. Emitter-biased LED
driver.
To calculate the h-parameters of a transistor in common
emitter configuration.
To calculate h-parameters of given transistor using data
sheet.
Build voltage regulator using 78XX and 79XX and
measure dropout voltage of the given voltage regulator.
Build variable voltage regulator using LM317 and
measure dropout voltage of the given voltage regulator.
Demonstration of working of UPS.
Mini project.
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Sign
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 1
AIM: To Use Multimeter For Measuring Electrical Parameters.
THEORY:
1. Function/Range Switch: selects the function (voltmeter, ammeter, or ohmmeter)
and the range for the measurement.
2. COM Input Terminal: Common ground, used in ALL measurements.
3. V Input Terminal: for voltage or resistance measurements.
4. 200 mA Input Terminal: for small current measurements.
5. 10 A Input Terminal: for large current measurements.
6. Low Battery LCD: appears when the battery needs replacement.
PRECAUTIONS FOR VOLTAGE MEASUREMENTS





Plug the black test lead into the COM jack.
Plug the red test lead into the V jack.
Set the function/range switch to either
DC volts in the upper left, or
AC volts in the upper right.
If you do not know the approximate voltage about to be measured, use the largest
voltage range available.
Connect the free ends of the red and black test leads ACROSS the device to the
measured. Voltage is always measured with the meter in PARALLEL with the device.
If the LCD displays either "1." or "-1." with all other digits blank, the voltage is
beyond the selected range. Use the switch to select a larger range.
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EC DEPARTMENT
ECA (3321101) SEM -2
Once you know the approximate voltage across the device, then use the switch to
select the lowest voltage range that will still accomodate the voltage across the device.
For example:
PICTURE OF A METER IN PARALLEL WITH DEVICE
Measure voltage and resistance this way:
FIGURE 1
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EC DEPARTMENT
ECA (3321101) SEM -2
PRECAUTIONS FOR CURRENT MEASUREMENTS





Turn the power off to the device and discharge any capacitors.
Plug the black test lead into the COM jack.
Plug the red test lead into either the
200 mA jack for small current measurements, or the
10 A jack for large current measurements.
If you do not know the approximate current about to be measured, use the 10 A jack.
Set the function/range switch to either DC amperes in the lower right, or AC amperes
in the middle right.
Break open the circuit at the point where you want to measure the current by
removing one of the wires.
PICTURE OF A METER IN SERIES WITH DEVICE
Measure current this way:
FIGURE 2
Connect the free end of the red test lead to one place at which the wire was attached.
Connect the free end of the black test lead to the other place at which the wire was
attached. Current is always measured with the meter in SERIES with the device. If
you do not understand the difference between SERIES and PARALLEL, ask your
TA. Using the current meter incorrectly will blow the fuse or damage the meter.
Reapply the power to the device.
If the LCD displays either "1." or "-1." with all other digits blank, the current is
beyond the selected range. Use the switch to select a larger range.
Once you know the approximate current through the device, then use the switch to
select the lowest current range that will still accomodate the current through the
device.
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EC DEPARTMENT
ECA (3321101) SEM -2
Turn the power off to the device before removing the meter from the circuit.
PRECAUTIONS FOR RESISTANCE MEASUREMENTS




Turn the power off to the device and discharge any capacitors!
Plug the black test lead into the COM jack.
Plug the red test lead into the V jack.
Set the function/range switch to ohms ( ) in the lower left.
If you do not know the approximate resistance about to be measured, use the largest
range available.
Connect the free ends of the red and black test leads ACROSS the device to the
measured. Resistance is always measured with the meter in PARALLEL with the
device.
If the LCD displays either "1." or "-1." with all other digits blank, the resistance is
beyond the selected range. Use the switch to select a larger range.
Once you know the approximate resistance of the device, then use the switch to select
the lowest range that will still accommodate the resistance of the device.
CONCLUSION:
6
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 2
AIM: To study the different waveforms, to measure peak and rms voltages and the
frequency of A.C.
APPARATUS:


Oscilloscope,
Function Generator
THEORY:
Cathode ray oscilloscope is one of the most useful electronic equipment, which gives
a visual representation of electrical quantities, such as voltage and current waveforms
in an electrical circuit. It utilizes the properties of cathode rays of being deflected by
an electric and magnetic fields and of producing scintillations on a fluorescent screen.
Since the inertia of cathode rays is very small, they are able to follow the alterations
of very high frequency fields and thus electron beam serves as a practically inertia
less pointer. When a varying potential difference is established across two plates
between which the beam is passing, it is deflected and moves in accordance with the
variation of potential difference. When this electron beam impinges upon a
fluorescent screen, a bright luminous spot is produced there which shows and follows
faithfully the variation of potential difference.
When an AC voltage is applied to Y-plates, the spot of light moves on the screen
vertically up and down in straight line. This line does not reveal the nature of applied
voltage waveform. Thus to obtain the actual waveform, a time-base circuit is
necessary. A time-base circuit is a circuit which generates a saw-tooth waveform. It
causes the spot to move in the horizontal and vertical direction linearly with time.
When the vertical motion of the spot produced by the Y-plates due to alternating
voltage, is superimposed over the horizontal sweep produced by X-plates, the actual
waveform is traced on the screen.
PROCEDURE:
STUDY OF WAVEFORMS:
To study the waveforms of an A.C voltage, it is led to the y – plates and the time base
voltage is given to the X-plates. The size of the figure displayed on the screen, can be
adjusted suitably by adjusting the gain controls. The time base frequency can be
changed, so as to accommodate one, two or more cycles of the signal. There is a
provision in C.R.O to obtain a sine wave or a square wave or a triangular wave.
MEASUREMENT OF D.C.VOLTAGE:
Deflection on a CRO screen is directly proportional to the voltage applied to the
deflecting plates. Therefore, if the screen is first calibrated in terms of known voltage.
i.e. the deflection sensitivity is determined , the direct voltage can be measured by
applying it between a pair of deflecting plates. The amount of deflection so produced
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EC DEPARTMENT
ECA (3321101) SEM -2
multiplied by the deflection sensitivity, gives the value of direct voltage.
MEASUREMENT OF A.C VOLTAGE:
To measure the alternating voltage of sinusoidal waveform, The A.C. signal, from the
signal generator, is applied across the y – plates. The voltage (deflection) sensitivity
band switch (Y-plates) and time base band switch (Xplates) are adjusted such that a
steady picture of the waveform is obtained on the screen.
The vertical height (l) i.e. peak-to-peak height is measured. When this peak-to-peak
height (l) is multiplied by the voltage (deflection) sensitivity (n) i.e. volt/div, we get
the peak-to-peak voltage (2Vo). From this we get the peak voltage (Vo). The rms
voltage Vrms is equal to Vo/ 2. This rms voltage Vrms is verified with rms voltage
value, measured by the multi-meter.
MEASUREMENT OF FREQUENCY:
An unknown frequency source (signal generator) is connected to y- plates of C.R.O.
Time base signal is connected to x – plates (internally connected). We get a sinusoidal
wave on the screen, after the adjustment of voltage sensitivity band switch (Y-plates)
and time base band switch (X-plates). The horizontal length (l) between two
successive peaks is noted. When this horizontal length (l) is multiplied by the time
base (m) i.e. sec/div , we get the time-period(T).The reciprocal of the timeperiod(1/T) gives the frequency(f). This can be verified with the frequency, measured
by the multi-meter.
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GP GANDHINAGAR
EC DEPARTMENT
CONCLUSION:
9
ECA (3321101) SEM -2
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 3
AIM: To Design Diode Clıppıng Cırcuıts And Observe İnput-Output Waveforms.
APPARATUS:



Oscilloscope, DC Power Supply, Function Generator
Resistors
Diodes
THEORY:
Clipping networks are designed to limit the positive and/or negative parts of the input
waveform to a predetermined value. As a result, the shape of the signal at the output is
different than the input.
DIODE VOLTAGE CLIPPERS
We are going to use the piecewise linear model of the diode :
(a)
(b)
Figure 3.1
Where V is the cut-in voltage (forward voltage drop) of the diode and R D represents
the equivalent dynamic resistance (a linear approximation to the real curve).
For VD < V diode will be assumed open circuit.
For VD  V the equivalent circuit is shown in Fig.3.1.b
Now consider the circuit in Fig.3.2.a. If the diode is replaced by its piecewise linear
model, the circuit in Fig.3.3.b is obtained for Vin(t) VB+V and diode is open-circuit
when Vin(t)<VB+V.
(a)
(b)
Figure 3.2
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EC DEPARTMENT
ECA (3321101) SEM -2
For Vin(t)<VB+V, it is obvious that Vo(t)=Vin(t)
For Vin(t)VB+V, Vo can be expressed as below :
Vo(t)=VB+V+[Vin(t)-(VB+V)] x RD / (R+RD)
When RD<<R then : Vo=VB+V (for ideal diode Vo=VB)
The transfer characteristic is piecewise linear and continuous and has a corner point at
VB+V. In order to obtain a good clipper, the optimum value of the resistor should be
chosen such that : RS<<R<<RL where RS is the source resistance of the signal
generator and RL is the load resistor.
In Fig.3.3 you can see the transfer characteristics of the clipper and an example inputoutput combination (RD=Rf).
Slope=RD/(RD+R)
Figure 3.3
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EC DEPARTMENT
PROCEDURE :
1.
2.
3.
4.
Make connections as per circuit-diagram.
Switch on the trainer kit.
Apply input signal from the function generator.
Observe input-output waveforms on CRO.
WAVEFORMS :
CONCLUSION :
12
ECA (3321101) SEM -2
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 4
AIM: To Design Diode Clamping Circuits And Observe Input-Output Waveforms.
APPARATUS:



Oscilloscope, DC Power Supply, Function Generator
Resistors, Capacitor
Diodes
THEORY:
Clamping circuits shift the signal to a predetermined level, while preserving its
original form.
DIODE VOLTAGE CLAMPERS
In a clamping circuit, the input waveform is clamped (shifted) to a reference
voltage when the shape is usually preserved. Clamping circuits have three elements. A
capacitor, a resistor and a diode. R and C are chosen such that the RC time constant is
large enough to ensure that the capacitor voltage remains practically constant during
one period of the input waveform.
Figure 4.1
In Fig.4.1 a negative clamping circuit (positive excursions of the input signal are
brought to the clamping level, the output signal is below the clamping level) is
formed. Assuming an ideal diode and an ideal voltage source, the drop across the
diode is zero when forward biased. Therefore the output can not rise above zero and is
clamped to this level.
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EC DEPARTMENT
ECA (3321101) SEM -2
Figure 4.2
When the input voltage is positive, the diode is conductive and the diode current
charges the capacitor and generates DC voltage, VR, across the resistor R. The
capacitor voltage input voltage until th positive peak Vm is reached. At this point, the
voltage across the capacitor is equal to the peak value of the input voltage,Vm. When
the input falls below Vm, the capacitor voltage exceeds the input voltage and the
diode is OFF. Assuming ideal operation, from this point on, the diode is always
reverse biased and the capacitor maintains its voltage. The output voltage is therefore
just a shifted version of the input to -Vm.
Vo=Vin(t)-VC=Vin(t)-Vm
PROCEDURE:
5.
6.
7.
8.
Make connections as per circuit-diagram.
Switch on the trainer kit.
Apply input signal from the function generator.
Observe input-output waveforms on CRO.
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EC DEPARTMENT
WAVEFORMS :
CONCLUSION:
15
ECA (3321101) SEM -2
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 5
AIM: Obtain V-I Characteristics Of Zener Diode.
APPARATUS:
THEORY:
Under specific fabrication conditions, a diode may be created that will not be
destroyed if the breakdown voltage is exceeded, as long as the current does not
exceed a defined maximum (to prevent overheating). These devices are known as
zener diodes and they are designed to have an avalanche characteristic that is very
steep.
In the forward bias region, the zener behaves like a regular diode within specified
current and/or power limits. The magic of these devices comes in when we get into
the reverse bias region. As previously mentioned, the zener is designed to have an
almost vertical avalanche characteristic at the breakdown voltage – hereinafter also
called the zener voltage, and it is ideal for use in voltage regulation. The limiting
(maximum) power for a zener diode is given by Pz=Vz*Izmax and is a function of the
design and construction of the diode. The knee of the curve (the current for which
|vD|=VZ) is generally approximated as 10% of Izmax, or Izmin=0.1Izmax.
There are two distinctly different mechanisms that may cause breakdown in a zener
diode:
1. Above approximately eight (8) volts, the predominant mechanism is avalanche
breakdown, also referred to as impact ionization or avalanche multiplication. This
process begins with thermally generated minority carriers that acquire enough kinetic
energy to break covalent bonds and create an EHP through collisions with crystal
atoms. The free carriers created through this collision contribute to the reverse current
and may also possess enough energy to participate in collisions, creating further EHPs
and the avalanche effect.
2. The high field emission or zener breakdown mechanism is the second method of
disrupting the covalent bonds of the crystal and increasing the reverse bias diode
current. The reverse voltage where this occurs is determined by the diode doping and
occurs when the depletion layer field is large enough to break covalent bonds and
cause the number of free carriers due to EHP generation to multiply.
Either of these effects, or a combination of the two, significantly increases the
current in the reverse bias region while having a negligible effect in the voltage drop
across the junction. Although “breakdown” and “disruption” and words of that order
have been liberally used in the previous discussion, please realize that the zener
process in not inherently destructive unless the maximum power dissipation specified
for the device is exceeded.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
CIRCUIT DIAGRAM:
Figure5.1(a) Zener diode forward bias.
forward bias.
Figure5.1(b) Zener diode
Figure-5.2 V-I characteristics of zener diode
PROCEDURE:
Step-1 Connect the circuit as per shown in figure-5.1(a) and figure-5.1(b) one by
one.
Step-2 First for forward bias figure-5.1(a),increase the input and check voltage
across load and current through zener diode
Step-3 Do the same procedure as done in step-5.2 by changing the position of zener
diode as shown in figure-5.1(b). Means take reading for reverse bias
condition
Step-4 Draw the V-I Characteristics for taken reading of voltage across zener diode
and current through zener diode.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
OBSERVATION TABLE
Sr. no
Input voltage
Output voltage
Voltage across zener
diode
CONCLUSION:
18
Current through zener
diode
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 6
AIM: Design Voltage Regulator For Given Value Of Regulated Voltage Using Zener
Diode.
APPARATUS:
THEORY:
This ability to control itself can be used to great effect to regulate or stabilize a
voltage source against supply or load variations. The fact that the voltage across the
diode in the breakdown region is almost constant turns out to be an important
application of the zener diode as a voltage regulator
As mentioned earlier, the characteristics of the zener diode make it ideal for
application as a voltage regulator. Placing the zener diode in parallel with the load as
shown in Figure -6.1 (reproduced to the right) ensures an essentially constant output
voltage even source voltage may vary. The key to the design of this voltage regulator
is to choose the resistor Ri to keep the zener diode in the breakdown region, while
ensuring that the diode current never exceeds Izmax.
Now we derive the expression for this circuit parameter by developing the nodal
expression for the zener current and defining the two extremes for iZ in terms of the
input/output conditions:
1. Izmin occurs when the load current is maximum and the source voltage is
minimum.
2. Izmax occurs when the load current is minimum and the source voltage is
maximum.
CIRCUIT DIAGRAM
Figure-6.1 Zener diode as voltage regulator
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EC DEPARTMENT
ECA (3321101) SEM -2
PROCEDURE:
Step-1
Step-2
Step-3
Step-4
Step-5
Connect the circuit as per shown in figure-6.1.
Vary the input voltage and take the output v0 at load RL.
Check the voltage after which voltage across zener diode does not change.
Also take the reading of the Iz and IL.
Repeat the Procedure after changing the value of Ri.
OBSERVATION TABLE :
Sr.
no
Input voltage
Output voltage
at RL
Voltage across
zener diode
CONCLUSION:
20
Current through
zener diode
Current through
RL
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT - 7
AIM: Obtain V-I Characteristics of Photo diode.
APPARATUS:
THEORY:
Figure 7.1: P-N JUNCTION PHOTO DIODE
Three major types of photodiodes are available in the market:
(i)
PN junction photo diode,
(ii)
PIN junction photo diode, and
(iii) Avalanche photo diode (APD).
P-N junction photodiodes comprise a two-electrode, radiation-sensitive P-N junction
formed in a semiconductor material in which the reverse current varies with the
amount of illumination. PIN junction photodiodes are diodes with a large intrinsic
region sandwiched between p-doped and n-doped semiconducting regions. Photons
absorbed in this region create electron-hole pairs that are then separated by an electric
field, thus generating an electric current in a load circuit.
Avalanche photodiodes are devices that utilize avalanche multiplication of current by
means of hole-electron pairs created by absorbed photons. When the reverse-bias
voltage of the device approaches the breakdown level, the hole-electron pairs collide
with ions to create additional hole-electron pairs, thus resulting in the signal gain.
The photodiode spectral response can be measured in X-ray, UV, visible, or IR
regions of the Electromagnetic spectrum. X-ray photodiodes are optimized for X-ray,
gamma ray, and beta Radiation detection. UV enhanced photodiodes are optimized
for the UV and blue spectral Regions, which requires special fabrication processes.
Visible photodiodes operate in the visible range. Figure shows the PN-junction Photo
Diode used in this experiment.
A photo diode behaves like a current source when illuminated. When operated
without bias, the
Current is distributed between the shunt resistance and external load resistor. In this
mode, a Voltage is developed which creates forward bias, thus reducing its ability to
remain as a constant current source. When operated with reverse bias, the photo diode
becomes an ideal current source.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
PRINCIPLE OF OPERATION:
A photodiode is a P-N junction or PIN structure. When a photon of sufficient energy
strikes the diode, it creates an electron-hole pair. This mechanism is also known as the
inner photoelectric effect. If the absorption occurs in the junction's depletion region,
or one diffusion length away from it, these carriers are swept from the junction by the
built-in electric field of the depletion region. Thus holes move toward the anode, and
electrons toward the cathode, and a photocurrent is produced. The total current
through the photodiode is the sum of the dark current (current that flows
with or without light) and the photocurrent, so the dark current must be minimized to
maximize the sensitivity of the device.
PHOTOVOLTAIC MODE:
When used in zero bias or photovoltaic mode, the flow of photocurrent out of the
device is restricted and a voltage builds up. This mode exploits the photovoltaic
effect, which is the basis for solar cells – a traditional solar cell is just a large area
photodiode.
PHOTOCONDUCTIVE MODE:
In this mode the diode is often reverse biased (with the cathode driven positive with
respect to the anode). This reduces the response time because the additional reverse
bias increases the width of the depletion layer, which decreases the junction's
capacitance. The reverse bias also increases the dark current without much change in
the photocurrent. For a given spectral distribution, the photocurrent is linearly
proportional to the illuminance .
Although this mode is faster, the photoconductive mode tends to exhibit more
electronic noise. The leakage current of a good PIN diode is so low (<1 nA) that the
Johnson–Nyquist noise of the load resistance in a typical circuit often dominates.
OTHER MODE OF OPERATION
AVALANCHE PHOTODIODES:
Avalanche photodiodes have a similar structure to regular photodiodes, but they are
operated with much higher reverse bias. This allows each photo-generated carrier to
be multiplied by avalanche breakdown, resulting in internal gain within the
photodiode, which increases the effective responsivity of the device.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
CIRCUIT DIAGRAM:
Figure 7.2: CIRCUIT DIAGRAM OF PHOTO DIODE.
PROCEDURE:
Step-1
Step- 2
Step-3
Connect the circuit as per shown in figure-7.2.
Set one Fix value of input to Photo Diode and Vary the LED power.
Repeat step-2 for setting various input voltage and measure LED power at
which Photo Diode
conducts.
Step-4 Draw the V-I characteristics for taken reading of voltage across Photo Diode
and current through Photo Diode.
OBSERVATION TABLE:
Sr. no
Input voltage
LED Power
Voltage across Photo
Diode
CONCLUSION:
23
Current through Photo
Diode
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT – 8
AIM: Obtain V-I Characteristics Of LDR Using Suitable Example.
APPARATUS:
THEORY:
Figure 8.1: Light Dependent Resistor
An LDR is a component that has a resistance that changes with the light intensity that
falls upon it. They have a resistance that falls with an increase in the light intensity
falling upon the device.
The resistance of an LDR may typically have the following resistances
Daylight = 5000Ω
Dark = 20000000 Ω
You can therefore see that there is a large variation between these figures. If you
plotted this variation on a graph you would get something similar to that shown by the
graph to the right.
Figure-8.2 CHARACTERISTICS OF LDR
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EC DEPARTMENT
ECA (3321101) SEM -2
APPLICATIONS
There are many applications for Light Dependent Resistors. These include:
1) Lighting switch
The most obvious application for an LDR is to automatically turn on a light at
certain light level. An example of this could be a street light.
2) Camera shutter control
LDRs can be used to control the shutter speed on a camera. The LDR would
be used the measure the light intensity and the set the camera shutter speed to
the appropriate level.
CIRCUIT DIAGRAM:
Figure-8.2: CIRCUIT DIAGRAM FOR LDR CHARACTERISTICS WITH
EXAMPLE
PROCEDURE:
Step-1 Connect the circuit as per shown in figure-8.2.
Step-2 Set the voltage Vcc.
Step-3 Vary the light Intensity on LDR. Check the value of resistance of LDR for
Light Intensity change.
Step-4 Plot the graph of resistance v/s Light intensity.
Step-5 And also check that at what value of LDR the Transistor is ON.
OBSERVATION TABLE:
Sr.
no
Value of Vcc
Power of LED Value of LDR
CONCLUSION:
25
Status of
Transistor(On/Off)
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EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 9
AIM: To study transistor as a switch, as a base-biased led driver.
APPARATUS:
 Transistor,
 LED,
 Resistors,
THEORY:
Base bias is useful in digital circuits because these circuits are usually designed to
operate at saturation and cutoff. Because of this, they have either low output voltage
or high output voltage.
The base current is zero in Fig.1 which means the transistor is at cutoff. When the
switch is closed to supply voltage, transistor goes into hard saturation.
CIRCUIT DIAGRAM:
R2
1.5k
D1
LED2
S1
R1
15k
+ V2
15V
Q1
NPN
+ V1
15V
FIGURE9.1 (a) Base-biased LED Driver
PROCEDURE:
Step-1
Step-2
Connect the circuit as per shown in figure-9.1(a).
First connect S1 switch to ground, so no base current and transistor is in
cutoff. LED will be off.
Step-3 Connect S1 switch to supply voltage, transistor is in hard saturation. LED
will be ON.
Step-4 Also measure input current IB, output current IC and output voltage VCE.
Step-5 To change LED current in the circuit, change either collector resistance or
collector supply voltage.
OBSERVATION TABLE:
Sr.
no
Input current (IB)
Theoretical
Practical
CONCLUSION:
26
Output current (IC)
Output voltage
(VCE )
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 10
AIM: CB Characteristics Of A Transistor.
APPARATUS:
 NPN-Transistor – BC107
 Regulated Power supply - (0-15V)
 Resistor - 1KΩ
 Ammeter - (0-200mA)
 Voltmeter - (0-20V)
 Connecting wires
THEORY:
A transistor is a three terminal active device. The terminals are emitter, base,collector.
In CB configuration, the base is common to both input (emitter) and output
(ollector). For normal operation, the E-B junction is forward biased and C-B junction
is reverse biased.
In CB configuration, IE is +ve, IC is –ve and IB is –ve. So,
VEB = f1 (VCB, IE) and
IC = f2 (VCB, IE)
With an increasing the reverse collector voltage, the space-charge width at the
output junction increases and the effective base width „W‟ decreases. This
phenomenon is known as “Early effect”. Then, there will be less chance for
recombination within the base region. With increase of charge gradient with in the
base region, the current of minority carriers injected across the emitter junction
increases. The current amplification factor of
CB configuration is given by,
α = ΔIC / ΔIE
27
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
CIRCUIT DIAGRAM:
INPUT CHARACTERSTICS:
OUTPUT CHARACTERSTICS:
PROCEDURE:
INPUT CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. For plotting the input characteristics, the output voltage VCB is kept constant
at 0V and for different values of VBE note down the values of IE.
3. Repeat the above step keeping VCB at 5V, 10V. All the readings are
tabulated.
4. A graph is drawn between VBE and IE for constant VCB.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
OUTPUT CHARACTERISTICS:
1. Connections are made as per the circuit diagram.
2. For plotting the output characteristics, the input IE is kept constant at 1mA and
for different values of VCB, note down the values of IC.
3. Repeat the above step for the values of IE at 2 mA, and 3 mA, all the readings
are tabulated.
4. A graph is drawn between VCB and IC for constant IE
OBSERVATIONS:
INPUT CHARACTERISTICS:
OUTPUT CHARACTERISTICS:
INPUT CHARACTERISTICS:
29
GP GANDHINAGAR
EC DEPARTMENT
OUTPUT CHARACTERISTICS:
CONCLUSION:
30
ECA (3321101) SEM -2
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 11
AIM: CE Characteristics Of A Transistor
APPARATUS:
 NPN-Transistor – BC107
 Regulated Power supply - (0-15V)
 Resistor - 1KΩ
 Ammeter - (0-200mA)
 Voltmeter - (0-20V)
 Connecting wires
THEORY:
A transistor is a three terminal device. The terminals are emitter, base, collector. In
common emitter configuration, input voltage is applied between base and emitter
terminals and output is taken across the collector and emitter terminals. Therefore the
emitter terminal is common to both input and output.
The input characteristics resemble that of a forward biased diode curve. This is
expected since the Base-Emitter junction of the transistor is forward biased. As
compared to CB arrangement IB increases less rapidly with VBE. Therefore input
resistance of CE circuit is higher than that of CB circuit.
The output characteristics are drawn between Ic and VCE at constant IB. the collector
current varies with VCE unto few volts only. After this the collector current becomes
almost constant, and independent of VCE. The value of VCE up to which the
collector current changes with V CE is known as Knee voltage. The transistor always
operated in the region above Knee voltage, IC is always constant and is approximately
equal to IB.
The current amplification factor of CE configuration is given by
Β = ΔIC/ΔIB
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
CIRCUIT DIAGRAM:
INPUT CHARACTERSTICS:
OUTPUT CHARACTERSTICS:
PROCEDURE:
INPUT CHARECTERSTICS:
1. Connect the circuit as per the circuit diagram.
2. For plotting the input characteristics the output voltage VCE is kept constant at 0V
and for different values of VBE. Note down the values of IC
3. Repeat the above step by keeping VCE at 5V and 8V.
4. Tabulate all the readings.
5. Plot the graph between VBE and IB for constant VCE
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EC DEPARTMENT
ECA (3321101) SEM -2
OUTPUT CHARACTERSTICS:
1. Connect the circuit as per the circuit diagram
2. For plotting the output characteristics the input current IB is kept constant at 10Μa
and for
different values of VCE note down the values of IC
3. Repeat the above step by keeping IB at 20μA, 60μA
4. Tabulate the all the readings
5. Plot the graph between VCE and IC for constant IB
OBSERVATIONS:
INPUT CHARACTERISTICS:
OUTPUT CHARACTERISTICS:
INPUT CHARACTERISTICS:
33
GP GANDHINAGAR
EC DEPARTMENT
OUTPUT CHARACTERISTICS:
CONCLUSION:
34
ECA (3321101) SEM -2
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 12
AIM: To study Transistor biasing, a voltage divider bias.
APPARATUS:
 Transistor,
 Resistors,
 Power supply.
THEORY:
A prototype is a basic circuit that designer can modify to get more advanced circuits.
Base bias is a prototype used in design of digital circuits. Emitter bias is a prototype
used in design in amplifier circuits.
The most famous circuit based on the emitter bias prototype is voltage divider bias.
CIRCUIT DIAGRAM:
R1
10k
RC
3.6k
+ Vcc
10V
Q1
NPN
R2
2.2k
RE
1k
FIGURE12.1 (a) Voltage divider-biased
PROCEDURE:
Step-1
Step-2
Connect the circuit as per shown in figure-11.1(a).
Measure input voltage VB, input current IB, output current IC and output
voltage VCE.
Step-3 Compare theoretical and practical values for analysis.
Step-4 To change RE = 2 kΩ in the circuit, base voltage VB unaffected; emitter
voltage VE remain same, emitter resistance doubled so emitter current IE
decrease to half and VCE is increase.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
OBSERVATION TABLE :
1.
2.
3.
4.
5.
6.
Divider Current: I=VCC/R1+R2
Base Voltage: VB=IR2
Emitter Voltage: VE=VB - VBE
Emitter Current: IE=VE/RE
Collector Voltage: VC=VCC ICRC
Collector –Emitter Voltage:
VCE=VC-VE
RE = 1 kΩ
Theoretical Practical
0.82 mA
1.8 V
1.1 V
1.1 mA
6.04 V
RE = 2 kΩ
Theoretical Practical
0.82 mA
1.8 V
1.1 V
0.55 mA
8.02 V
4.94 V
6.92 V
CONCLUSION:
36
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 13
AIM: To study single stage transistor amplifier frequency response.
a. To measure the voltage gain of CE amplifier
b. To draw the frequency response curve of CE amplifier
APPARATUS:
THEORY:
The CE amplifier provides high gain &wide frequency response. The emitter lead is
common to both input & output circuits and is grounded. The emitter-base circuit is
forward biased. The collector current is controlled by the base current rather than
emitter current. The input signal is applied to base terminal of the transistor and
amplifier output is taken across collector terminal. A very small change in base
current produces a much larger change in collector current.
When +VE half-cycle is fed to the input circuit, it opposes the forward bias of the
circuit which causes the collector current to decrease, it decreases the voltage more –
VE.
Thus when input cycle varies through a -VE half-cycle, increases the forward bias of
the circuit, which causes the collector current to increases thus the output signal is
common emitter amplifier is in out of phase with the input signal.
CIRCUIT DIAGRAM:
FIGURE 13.1 Circuit diagram
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
PROCEDURE:
1. Connect the circuit as shown in circuit diagram.
2. Apply the input of 20mV peak-to-peak and 50Hz frequency using function
generator.
3. Measure the Output Voltage VO (p-p).
4. Tabulate the readings in the tabular form.
5. The voltage gain can be calculated by using the expression Av= (V0/Vi)
6. For plotting the frequency response the input voltage is kept Constant at 20mV
peak-to
peak and the frequency is varied from 50Hz to 1MHz Using function
generator.
7. All the readings are tabulated and voltage gain in dB is calculated by using the
expression
Av=20 log10 (V0/Vi)
8. A graph is drawn by taking frequency on x-axis and gain in dB on y-axis on Semilog graph.
The band width of the amplifier is calculated from the graph using the expression,
Bandwidth, BW=f2-f1
Where f1 is the lower cut-off frequency of CE amplifier, and
Where f2 is the upper cut-off frequency of CE amplifier
The bandwidth product of the amplifier is calculated using the expression
Gain Bandwidth product = (3dB mid-band gain) X (Bandwidth)
OBSERVATIONS:
FREQUENCY RESPONSE:
Frequency in
(Hz)
Input Voltage (vi)
Output Voltage (vo)
MODEL WAVEFORMS:
INPUT WAVEFORM:
OUTPUT WAVEFORM:
38
Av
Gain in dB
Av = 20 log10
(v0/vi)
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
FREQUENCY RESPONSE:
CONCLUSION:
The voltage gain and frequency response of the CE amplifier are obtained.
39
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 14
AIM: RC COUPLED AMPLIFIER
1. To calculate voltage gain.
2. To observe frequency response of 2 stage RC coupled amplifier.
APPARATUS:
THEORY:
This is most popular type of coupling as it provides excellent audio fidelity. A
coupling capacitor is used to connect output of first stage to input of second stage.
Resistances R1, R2, RE form biasing and stabilization network. Emitter bypass
capacitor offers low reactance paths to signal coupling Capacitor transmits ac signal,
blocks DC.
Cascade stages amplify signal and overall gain is increased total gain is less than
product of gains of individual stages. Thus for more gain coupling is done and overall
gain of two stages equals to
A = A1 * A2
Where,
A1 = voltage gain of first stage
A2 = voltage gain of second stage.
When ac signal is applied to the base of the transistor, its amplified output appears
across the collector resistor RC. It is given to the second stage for further
amplification and signal appears with more strength. Frequency response curve is
obtained by plotting a graph between frequency and gain in dB .The gain is constant
in mid frequency range and gain decreases on both sides of the mid frequency range.
The gain decreases in the low frequency range due to coupling capacitor CC and at
high frequencies due to junction capacitance CBE.
CIRCUIT DIAGRAM:
40
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
PROCEDURE:
1. Apply input by using function generator to the circuit.
2. Observe the output waveform on CRO.
3. Measure the voltage at
a. Output of first stage
b. Output of second stage.
4. From the readings calculate voltage gain of first stage, second stage and overall
gain of two stages. Disconnect second stage and then measure output voltage of first
stage and calculate voltage gain.
5. Compare it with voltage gain obtained when second stage was connected.
6. Note down various values of gain for different frequencies.
7. A graph is plotted between frequency and voltage gain.
OBSERVATIONS:
Frequency in
(Hz)
Input Voltage (vi)
Output Voltage (vo)
Av
FREQUENCY RESPONSE:
CONCLUSION:
Thus voltage gain is calculated and frequency response is observed
41
Gain in dB
Av = 20 log10
(v0/vi)
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 15
AIM: To study Transistor as a switch, as a base-biased LED driver.
APPARATUS:
 Transistor,
 LED,
 Resistors,
THEORY:
Base bias is useful in digital circuits because these circuits are usually designed to
operate at saturation and cutoff. Because of this, they have either low output voltage
or high output voltage.
The base current is zero in Fig.1 which means the transistor is at cutoff. When the
switch is closed to supply voltage, transistor goes into hard saturation.
CIRCUIT DIAGRAM:
R2
1.5k
D1
LED2
S1
R1
15k
+ V2
15V
Q1
NPN
+ V1
15V
FIGURE15.1 (a) Base-biased LED Driver
PROCEDURE:
Step-1
Step-2
Connect the circuit as per shown in figure-9.1(a).
First connect S1 switch to ground, so no base current and transistor is in
cutoff. LED will be off.
Step-3 Connect S1 switch to supply voltage, transistor is in hard saturation. LED
will be ON.
Step-4 Also measure input current IB, output current IC and output voltage VCE.
Step-5 To change LED current in the circuit, change either collector resistance or
collector supply voltage.
OBSERVATION TABLE :
Sr.
no
Input current (IB)
Output current (IC)
Theoretical
Practical
CONCLUSION:
42
Output voltage (VCE
)
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 16
AIM: To study Transistor as a switch. Emitter-biased LED driver.
APPARATUS:
 Transistor,
 LED,
 Resistors.
THEORY:
Emitter bias is useful in digital circuits because these circuits are usually designed to
operate at active region.
The emitter current is zero in Fig.10.1 which means the transistor is at cutoff. When
the switch is closed to supply voltage, transistor goes into active region. Ideally,
emitter voltage is 15V. This means emitter current is 10mA. This time LED voltage
drop has no effect. It doesn’t matter whether the exact LED voltage is 1.8, 2 or 2.5V.
This is an advantage of the emitter biased over base biased design. LED current is
independent of the LED voltage. Also it doesn’t require collector resistor.
CIRCUIT DIAGRAM:
D1
LED2
S1
+ Vcc
15V
Q1
NPN
+ V1
15V
Re
1.5k
FIGURE16.1 (a) Emitter-biased LED Driver
PROCEDURE:
Step-1
Step-2
Connect the circuit as per shown in figure-10.1(a).
First connect S1 switch to ground, so no base current and transistor is in
cutoff. LED will be off.
Step-3 Connect S1 switch to supply voltage, transistor is in active region. LED will
be ON.
Step-4 Also measure input current IB, output current IC and output voltage VCE.
Step-5 To change LED current in the circuit, change either emitter resistance or
base supply voltage.
OBSERVATION TABLE :
Sr.
no
Input current (IB)
Output current (IC)
Theoretical
Practical
CONCLUSION:
43
Output voltage (VCE
)
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 17
AIM: To calculate the h-parameters of a transistor in common emitter configuration.
APPARATUS:
THEORY:
The two sets of characteristics are necessary to describe the behavior of the CE
configuration one for input or base emitter circuit and other for the output or collector
emitter circuit. In input characteristics the emitter base junction forward biased by a
very small voltage VBB whereas collector base junction reverse biased by a very
large voltage VCC. The input characteristics are a plot of input current IB versus the
input voltage VBE for a range of values of output voltage VCE. The following
important points can be observed from these characteristics curves.
1. The characteristics resemble that of CE configuration.
2. Input resistance is high as IB increases less rapidly with VBE
3. The input resistance of the transistor is the ratio of change in base emitter voltage
ΔVBE to change in base current ΔIB at constant collector emitter voltage (VCE) i.e...
Input resistance or input impedance
hie = ΔVBE / ΔIB at VCE constant.
OUTPUT CHARACTERISTICS:
A set of output characteristics or collector characteristics are a plot of output current
IC
VS output voltage VCE for a range of values of input current IB .The following
important points can be observed from these characteristics curves:The transistor always operates in the active region. I.e. the collector current
IC increases with VCE very slowly. For low values of the VCE the IC increases
rapidly with a small increase in VCE .The transistor is said to be working in saturation
region.
Output resistance is the ratio of change of collector emitter voltage ΔVCE , to change
in
collector current ΔIC with constant IB.
Output resistance or Output impedance hoe = ΔVCE /
ΔIC at IB constant.
1. Input Impedance hie = ΔVBE / ΔIB at VCE constant
2. Output impedance hoe = ΔVCE / ΔIC at IB constant
3. Reverse Voltage Gain hre = ΔVBE / ΔVCE at IB constant
4. Forward Current Gain hfe = ΔIC / ΔIB at constant VCE
In CB configuration, IE is +ve, IC is –ve and IB is –ve. So,
VEB = f1 (VCB, IE) and
IC = f2 (VCB, IE)
With an increasing the reverse collector voltage, the space-charge width at the output
junction
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EC DEPARTMENT
ECA (3321101) SEM -2
increases and the effective base width „W‟ decreases. This phenomenon is known as
“Early
effect”. Then, there will be less chance for recombination within the base region. With
increase of charge gradient with in the base region, the current of minority carriers
injected
across the emitter junction increases. The current amplification factor of CB
configuration is
given by,
α = ΔIC/ ΔIE
1. Input Impedance hib = ΔVBE / ΔIE at VCE constant
2. Output impedance hob = ΔIC / ΔVCE at IB constant
3. Reverse Voltage Gain hrb = ΔVBE / ΔVCB at IB constant
4. Forward Current Gain hfb = ΔIC / ΔIE at constant VCE
CIRCUIT DIAGRAM:
COMMON EMITTER CONFIGURATION:
INPUT CHARACTERISTICS:
OUTPUT CHARACTERISTICS:
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
PROCEDURE:
COMMON EMITTER CONFIGURATION:
1. Connect a transistor in CE configuration circuit for plotting its input and output
characteristics.
2. Take a set of readings for the variations in IB with VBE at different fixed values of
output
voltage VCE.
3. Plot the input characteristics of CE configuration from the above readings.
4. From the graph calculate the input resistance hie and reverse transfer ratio hre by
taking
the slopes of the curves.
5. Take the family of readings for the variations of IC with VCE at different values of
fixed IB.
6. Plot the output characteristics from the above readings.
7. From the graphs calculate hfe and hoe by taking the slope of the curves.
TABULAR COLUMNS:
COMMON EMITTER CONFIGURATION:
INPUT CHARACTERISTICS:
VCE = 0V
VBE(V)
IB(mA)
VCE = 5V
VBE(V)
IB(mA)
VCE = 8V
VBE(V)
IB(mA)
IB = 20 μA
VCE (V)
IC(mA)
IB = 60 μA
VCE (V)
IC(mA)
OUTPUT CHARACTERISTICS:
IB = 10 μA
VCE (V)
IC(mA)
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EC DEPARTMENT
ECA (3321101) SEM -2
MODEL GRAPHS:
COMMON EMITTER CONFIGURATION:
INPUT CHARACTERISTICS:
OUTPUT CHARECTERSTICS:
CONCLUSION:
The H-Parameters for a transistor in CE configuration are calculated from the input
and output characteristics.
1. Input Impedance hie = _____
2. Reverse Voltage Gain hre = _____
3. Forward Current Gain hfe = _____
4. Output conductance hoe = _____
47
GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
EXPERIMENT 18
AIM: To calculate h-parameters of given transistor using data sheet.
APPARATUS:
 Transistor 2N3904,
 Data Sheet.
THEORY:
When the transistor was invented, people knew very little about its internal operation.
Because of this, an approach known as the h parameters was initially used to analyze
and design transistor circuits. This is a mathematical approach that models the
transistor on what is happening at its terminals without regards for the physical
processes taking place inside the transistor. The h-parameters are too mathematical for
the most people. They have survived on data sheet.
H parameter equation for EC configuration is:
vbe= hie ib + hre vce ……………(1)
ic= hfe ib + hoe vce …………….. (2)
Where input voltage =vbe , input current = ib ,output voltage = vce ,output current =ic
When output voltage is zero by short circuiting the output terminal, then vce =0.
 Put vce =0 in equation (1), we get input impedance hie =vbe/ ib .

Put vce =0 in equation (2), we get forward current gain hfe =ic/ ib .
When input current is zero by open circuiting the input terminal, then ib =0.
 Put ib =0 in equation (1), we get reverse voltage gain hre =vbe/ vce .

Put ib =0 in equation (2), we get output admittance hoe =ic/ vce .
PROCEDURE:
Refer to the data sheet of a 2N3904 during the practical. The ac quantities labeled
“Small-signal Characteristics.” Data sheet find quantities labeled as hfe, hie, hre, and
hoe. These are called h parameters.
1. hfe is given, is identical to the ac current gain β=hfe. The data sheet lists a
minimum hfe of 100 and a maximum of 400. Therefore, current gain β may be
as low as 100 or as high as 400. These values are for a collector current of 1
mA and collector-emitter voltage of 10 V.
2. Another h parameter is the quantity hie. The data sheet give a minimum hie of 1
kΩ and a maximum of 10 kΩ.
3. Same way find other remaining h parameters hre, and hoe and list in
observation table.
4. Other quantities listed under “Small-signal Characteristics” section include fT,
Ci, Cob and NF.
a. fT gives information about the high frequency limitations on a 2N3904.
b. Ci and Cob are input and output capacitances of the device.
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GP GANDHINAGAR
EC DEPARTMENT
ECA (3321101) SEM -2
c. NF is noise figure; it indicates how much noise the 2N3904 produce.
OBSERVATION TABLE:
Sr.
no
Input Impedance hie
Min
Max
Unit
Forward Current
gain hfe
Min Max Unit
CONCLUSION:
49
Reverse Voltage
gain hre
Min Max Unit
Output Admittance hoe
Min
Max
Unit