BIRLA VISHVAKARMA MAHAVIDHYALA ELECTRONICS & COMMUNICATION DEPARTMENT AY - 2020-21(ODD) PRACTICAL FILE SUBJECT NAME: ELECTRONIC DEVICES & CIRCUITS (2EC02_LAB) YEAR: B. Tech (2nd Year) NAME:- Parth Raj Singh ID. No:- 19EC452 INDEX Sr. No Title 1 To obtain frequency response of single stage transistor amplifier. 2 To study frequency of single state and 2-stage direct coupled transistor amplifier. 3 To study and calculate frequency of Wien Bridge Oscillator. 4 To study UJT as an Relaxation Oscillator. 5 6 To generate square wave to triangular wave and triggering pulse using IC741 op-amp. Design precision rectifier using opAmp IC741 and verify its operation using measurements. 7 Design Schmitt trigger circuit using op- amp and take measurements. 8 Determine the efficiency of class-B push pull power amplifier. 9 To study the Astable Multi vibrator using the Op-Amp IC µ741. 10 To study about the 555 as an Astable Multi vibrator. EXPERIMENT-1 Aim:- To obtain frequency response of single stage transistor amplifier. Software:- Orcade Capture Circuit Diagram:- Theory:The single stage common emitter amplifier circuit shown below uses what is commonly called "Voltage Divider Biasing". The Base voltage (VB) can be easily calculated using the Thus the base voltage is fixed by biasing and independent of base current provided the current in the divider circuit is large compared to the base current. Thus assuming IB ≈0, one can do the approximate analysis of the voltage divider network without using the transistor gain, β, in the calculation. 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. A1=voltage gain of first stage A2=voltage gain of second stage. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- Thus we can observe a graph which is non-linear. EXPERIMENT-2 Aim:- To calculate voltage gain & observe frequency response of RC coupled amplifier. Software:- Orcade Capture Circuit Diagram:- 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. 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. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- Thus a sinosoidal waveform is observed. EXPERIMENT-3 Aim:- To study and calculate frequency response of wein bridge oscillator. Software:- Orcade Capture Circuit Diagram:- Theory:One of the simplest sine wave oscillators which uses a RC network in place of the conventional LC tuned tank circuit to produce a sinusoidal output waveform, is called a Wien Bridge Oscillator. The Wien Bridge Oscillator is so called because the circuit is based on a frequencyselective form of the Wheatstone bridge circuit. The Wien Bridge oscillator is a twostage RC coupled amplifier circuit that has good stability at its resonant frequency, low distortion and is very easy to tune making it a popular circuit as an audio frequency oscillator but the phase shift of the output signal is considerably different from the previous phase shift RC Oscillator. The Wien Bridge Oscillator uses a feedback circuit consisting of a series RC circuit connected with a parallel RC of the same component values producing a phase delay or phase advance circuit depending upon the frequency. At the resonant frequency ƒr the phase shift is 0o. Consider the circuit below. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors, opamp ic uA741 needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- Thus we can get a square waveform on performing the experiment. EXPERIMENT-4 Aim:- To study UJT as an Relaxation Oscillator. Software:- Orcade Capture Circuit Diagram:- Theory:UJT relaxation oscillator is a type of RC ( resistor-capacitor) oscillator where the active element is a UJT (uni-junction transistor). UJT is an excellent switch with switching times in the order of nano seconds. It has a negative resistance region in the characteristics and can be easily employed in relaxation oscillators. The UJT relaxation oscillator is called so because the timing interval is set up by the charging of a capacitor and the timing interval is ceased by the the rapid discharge of the same capacitor. Before going into the details of UJT relaxation oscillator let’s have a look at the uni junction transistor (UJT). Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- Thus an graph is observed in a different pattern form. EXPERIMENT-5 Aim:- To design Integrator and Differentiator circuit using op amp. Software:- Orcade Capture Circuit Diagram:Integrator:- Differentiator:- Theory:Differentiator A differentiator is an electronic circuit that produces an output equal to the first derivative of its input. The non-inverting input terminal of the op-amp is connected to ground. That means zero volts is applied to its non-inverting input terminal. According to the virtual short concept, the voltage at the inverting input terminal of opamp will be equal to the voltage present at its non-inverting input terminal. So, the voltage at the inverting input terminal of op-amp will be zero volts. The nodal equation at the inverting input terminal's node is − Cd(0−Vi)dt+0−V0R=0Cd(0−Vi)dt+0−V0R=0 = −CdVidt=V0R= −CdVidt=V0R = V0= −RCdVidt = V0=−RCdVidt If RC=1secRC=1sec, then the output voltage V0V0 will be − V0=−dVidtV0= −dVidt Thus, the op-amp based differentiator circuit shown above will produce an output, which is the differential of input voltage ViVi, when the magnitudes of impedances of resistor and capacitor are reciprocal to each other. Note that the output voltage V0V0 is having a negative sign, which indicates that there exists a 1800 phase difference between the input and the output. Integrator An integrator is an electronic circuit that produces an output that is the integration of the applied input. the non-inverting input terminal of the op-amp is connected to ground. That means zero volts is applied to its non-inverting input terminal. According to virtual short concept, the voltage at the inverting input terminal of opamp will be equal to the voltage present at its non-inverting input terminal. So, the voltage at the inverting input terminal of op-amp will be zero volts. The nodal equation at the inverting input terminal is − 0−ViR+Cd(0−V0)dt=00−ViR+Cd(0−V0)dt=0 = −ViR=CdV0dt= −ViR=CdV0dt = dV0dt=−ViRC= dV0dt=−ViRC = dV0=(−ViRC)dt= dV0=(−ViRC)dt Integrating both sides of the equation shown above, we get − ∫dV0=∫(−ViRC)dt∫dV0=∫(−ViRC)dt =V0=−1RC∫Vtdt= V0=−1RC∫Vtdt If RC=1secRC=1sec, then the output voltage, V0V0 will be − V0=−∫VidtV0=−∫Vidt So, the op-amp based integrator circuit discussed above will produce an output, which is the integral of input voltage ViVi, when the magnitude of impedances of resistor and capacitor are reciprocal to each other. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- Thus graphs are observed and difference in waveform is observed. EXPERIMENT-6 Aim:- To prepare precision rectifier using opamp and verify its operation using measurements. Software:- Orcade Capture Circuit Diagram:- Theory:The precision rectifier, also known as a super diode, is a configuration obtained with an operational amplifier in order to have a circuit behave like an ideal diode and rectifier.[1] It is very useful for high-precision signal processing. With the help of a precision rectifier the high-precision signal processing can be done very easily. The op-amp-based precision rectifier should not be confused with the power MOSFET-based active rectification ideal diode. One of the non-linear behaviors that is sometimes required in analog circuits is rectification. Rectification is a process of separating the positive and negative portions of a waveform from each other and selecting from them what part of the signal to retain. In the case of half-wave rectification, we can choose to keep one polarity while discarding the other. The circuit above accepts an incoming waveform and as usual with op amps, inverts it. However, only the positive-going portions of the output waveform, which correspond to the negative-going portions of the input signal, actually reach the output. The direct feedback diode shunts any negative-going output back to the "-" input directly, preventing it from being reproduced. The slight voltage drop across the diode itself is blocked from the output by the second diode. The second diode allows positive-going output voltage to reach the output. Furthermore, since the output voltage is taken from beyond the output diode itself, the op amp will necessarily compensate for any non-linear characteristics of the diode itself. As a result, the output voltage is a true and accurate (but inverted) reproduction of the negative portions of the input signal. Thus, this circuit operates as a precision half-wave rectifier. If Rf is equal to Rin as is the usual case, the output voltage will have the same amplitude as the input voltage. If you want to keep the positive-going portion of the input signal instead of the negative-going portion, simply reverse the two diodes. The result will be a negative-going copy of the positive part of the input signal. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- We can observe half waves graph as output. EXPERIMENT-7 Aim:- To design schmitt triggering circuit using opamp and take measurements. Software:- Orcade Capture Circuit Diagram:- Theory:In electronics, a Schmitt trigger is a comparator circuit with hysteresis implemented by applying positive feedback to the non inverting input of a comparator or differential amplifier. It is an active circuit which converts an analog input signal to a digital output signal. The circuit is named a "trigger" because the output retains its value until the input changes sufficiently to trigger a change. In the non-inverting configuration, when the input is higher than a chosen threshold, the output is high. When the input is below a different (lower) chosen threshold the output is low, and when the input is between the two levels the output retains its value. This dual threshold action is called hysteresis and implies that the Schmitt trigger possesses memory and can act as a bistable multivibrator (latch or flip-flop). There is a close relation between the two kinds of circuits: a Schmitt trigger can be converted into a latch and a latch can be converted into a Schmitt trigger. Schmitt trigger devices are typically used in signal conditioning applications to remove noise from signals used in digital circuits, particularly mechanical contact bounce in switches. They are also used in closed loop negative feedback configurations to implement relaxation oscillators, used in function generators and switching power supplies. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- A square waveform graph is observed. EXPERIMENT-8 Aim:- Determine the efficiency of class-B push-pull amplifier. Apparatus:- Transistors, resistors, push pull amplifier. Circuit Diagram:Theory:To improve the full power efficiency of the previous Class A amplifier by reducing the wasted power in the form of heat, it is possible to design the power amplifier circuit with two transistors in its output stage producing what is commonly termed as a Class B Amplifier also known as a push-pull amplifier configuration. Push-pull amplifiers use two “complementary” or matching transistors, one being an NPN-type and the other being a PNP-type with both power transistors receiving the same input signal together that is equal in magnitude, but in opposite phase to each other. This results in one transistor only amplifying one half or 180 o of the input waveform cycle while the other transistor amplifies the other half or remaining 180o of the input waveform cycle with the resulting “two-halves” being put back together again at the output terminal. Then the conduction angle for this type of amplifier circuit is only 180 o or 50% of the input signal. This pushing and pulling effect of the alternating half cycles by the transistors gives this type of circuit its amusing “push-pull” name, but are more generally known as the Class B Amplifier as shown below. Class B Push-pull Transformer Amplifier Circuit The circuit above shows a standard Class B Amplifier circuit that uses a balanced centertapped input transformer, which splits the incoming waveform signal into two equal halves and which are 180o out of phase with each other. Another center-tapped transformer on the output is used to recombined the two signals providing the increased power to the load. The transistors used for this type of transformer pushpull amplifier circuit are both NPN transistors with their emitter terminals connected together. Here, the load current is shared between the two power transistor devices as it decreases in one device and increases in the other throughout the signal cycle reducing the output voltage and current to zero. The result is that both halves of the output waveform now swings from zero to twice the quiescent current thereby reducing dissipation. This has the effect of almost doubling the efficiency of the amplifier to around 70%. Assuming that no input signal is present, then each transistor carries the normal quiescent collector current, the value of which is determined by the base bias which is at the cut-off point. If the transformer is accurately center tapped, then the two collector currents will flow in opposite directions (ideal condition) and there will be no magnetization of the transformer core, thus minimizing the possibility of distortion. When an input signal is present across the secondary of the driver transformer T1, the transistor base inputs are in “anti-phase” to each other as shown, thus if TR1 base goes positive driving the transistor into heavy conduction, its collector current will increase but at the same time the base current of TR2 will go negative further into cut-off and the collector current of this transistor decreases by an equal amount and vice versa. Hence negative halves are amplified by one transistor and positive halves by the other transistor giving this push-pull effect. Unlike the DC condition, these alternating currents are ADDITIVE resulting in the two output half-cycles being combined to reform the sine-wave in the output transformers primary winding which then appears across the load. Class B Amplifier operation has zero DC bias as the transistors are biased at the cutoff, so each transistor only conducts when the input signal is greater than the Baseemitter voltage. Therefore, at zero input there is zero output and no power is being consumed. This then means that the actual Q-point of a Class B amplifier is on the Vce part of the load line as shown below. Class B Output Characteristics Curves The Class B Amplifier has the big advantage over their Class A amplifier cousins in that no current flows through the transistors when they are in their quiescent state (ie, with no input signal), therefore no power is dissipated in the output transistors or transformer when there is no signal present unlike Class A amplifier stages that require significant base bias thereby dissipating lots of heat – even with no input signal present. So the overall conversion efficiency ( η ) of the amplifier is greater than that of the equivalent Class A with efficiencies reaching as high as 70% possible resulting in nearly all modern types of push-pull amplifiers operated in this Class B mode. Conclusion:- A class B push-pull amplifier and its efficiency is calculated. EXPERIMENT-9 Aim:- To study Astable Multi vibrator using opamp IC u741. Software:- Orcade Capture Circuit Diagram:- Theory:The astable multivibrator is also called as a free-running multivibrator. It has two quasi-stable states i.e. no stable state such. No external signal is required to produce the changes in state. The component values used to decide the time for which circuit remains in each state. Usually, as the astable multivibrator oscillates between two states, is used to produce a square wave. The circuit looks like a Schmitt trigger except that the input voltage is replaced by a capacitor. When V0is at Vsat, the feedback voltage is called the upper threshold voltage Vut. When V0is at -Vsat, the feedback voltage is called the lower threshold voltage Vlt . Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- A square waveform is observed. EXPERIMENT-10 Aim:- To study about IC-555 as an Astable Multi vibrator. Software:- Orcade Capture Circuit Diagram:- Theory:- An Astable Multivibrator can be designed by adding two resistors (RA and RB in circuit diagram) and a capacitor (C in circuit diagram) to the 555 Timer IC. These two resistors and the capacitor (values) are selected appropriately so as to obtain the desired ‘ON’ and ‘OFF’ timings at the output terminal (pin 3). So basically, the ON and OFF time at the output (i.e the ‘HIGH’ and ‘LOW’ state at the output terminal) is dependent on the values chosen for RA,RB and C. We will see more about this on the astable multivibrator design section given below. The basic objective of an astable multivibrator is to switch the output status (from HIGH to LOW and from LOW to HIGH) at the desired time intervals, without any external intervention (say an input trigger pulse like in the case of monostable multivibrator). We achieve this (in a 555 IC) by controlling the discharge terminal (pin 7) of 555 IC through a capacitor (C). Inside the 555 IC, this discharge terminal (pin 7) is connected to the collector terminal of a transistor whose base is directly connected to the output terminal (non inverting terminal – Q) of SR flip flop. You have to notice that Vout (pin 3 – output terminal of 555 IC) is taken from the inverting output terminal (Q complimentary terminal) of SR flip flop. So when when flip flop output (non inverting) Q is HIGH, Vout will be LOW and when flip flop output Q is LOW, Vout will be HIGH. Procedure:1. Open Orcade Capture. 2. Create new page and give a name to it. 3. Insert the components such as resistors, transistor, capacitors needed for the circuit. 4. Give a connection to them through wire. 5. Create new stimulation profile and give the voltage/current marker at the point which it is to be measured. 6. Observe the Graph. Observation:- Conclusion:- A square waveform is observed with triangular waveform in the output.
