Amplifiers
An electronic amplifier, amplifier, or amp- is an electronic device that
increases the power of a signal.
[http://en.wikipedia.org/wiki/]
A
A Wheatstone
Wheatstone bridge
bridge
A Wheatstone bridge is an electrical circuit used to measure an
unknown electrical resistance by balancing two legs of a bridge
circuit.
A
R1
R3
C
D
Vcc
Vg
R2
Rx
B
Rx is the unknown resistance to be measured. R1, R2 and R3 are
resistors of known resistance and the resistance R2 is adjustable. If the
ratio of the two resistances R2 / R1 is equal to the ratio of Rx / R3, then
the voltage between the two midpoints; C and D will be zero.
A
A Wheatstone
Wheatstone bridge
bridge
At the point of balance, the ratio of:
R 2 Rx
=
R1 R3
R2
Rx =
R3
R1
If all resistor values and the supply voltage (Vcc) are known, and the
resistance of the galvanometer is high, the voltage across the bridge
(Vg) can be found by working out the voltage from each potential divider
and subtracting one from the other. The equation for this is:
Rx
R2
Vg = (
−
)Vcc
R3 + Rx R1 + R 2
B
ridge C
ircuits
Bridge
Circuits
Resistive elements are some of the most common sensors.
Sensor elements' resistances can range from less than 100Ω to
several hundred kΩ, depending on the sensor design and the physical
environment to be measured.
Resistance of popular sensors:
-Strain Gages (czujniki naprężenia) 120Ω , 350Ω , 3500Ω
-Pressure Sensors (czujniki ciśnienia) 350Ω - 3500Ω
-Relative Humidity (czujniki wigotności) 100kΩ - 10MΩ
-Resistance Temperature Devices (czujniki temperatury) 100Ω ,
1000Ω
-Thermistors (termistory) 100Ω - 10MΩ
[www.analog.com]
B
ridge C
ircuits
Bridge
Circuits
The basic Wheatstone bridge
[www.analog.com]
B
ridge C
ircuits
Bridge
Circuits
Bridge Circuits
In many bridge applications, there may be two, or even four elements
which vary.
Four commonly used bridges suitable for sensor applications.
[www.analog.com]
Amplifiers
Amplifiers
R
R Vcc
+
R
K
Vout
R
Bridge Amplifier
The Differential Amplifier circuit is a very useful op-amp circuit and by
adding more resistors in parallel with the input resistors R1 and R3, the
resultant circuit can be made to either "Add" or "Subtract" the voltages
applied to their respective inputs. One of the most common ways of
doing this is to connect a "Resistive Bridge" commonly called a
Wheatstone Bridge to the input of the amplifier.
[http://www.electronics-tutorials.ws]
Amplifiers
Amplifiers
Thermistor
t
R1 Vcc
Rf
V- - K
V+ +
P
Adjust
Relay
D
Vcc
R3
R2
Temperature Activated Switch
The circuit acts as a temperature-activated switch which turns the output
relay either "ON" or "OFF" as the temperature level detected by the
thermistor exceeds or falls below a pre-set value at V+ determined by
the position of P.
Amplifiers
Amplifiers
Instrumentation Amplifier
Instrumentation Amplifiers (in-amps) are very high gain differential
amplifiers which have a high input impedance and a single ended output.
Instrumentation amplifiers are mainly used to amplify very small
differential signals from strain gauges, thermocouples or current sensing
devices in motor control systems.
The instrumentation amplifier also has a very good common mode
rejection ratio, CMRR (zero output when V1 = V2) well in excess of
100dB at DC.
[http://www.electronics-tutorials.ws]
Amplifiers
Amplifiers
V1
Va
+
K1
R2
RB
RA
-
R1
R2
RA
K3
+
Vout
Vb
-
V2
K2
+
RB
High Input Impedance Instrumentation Amplifier
[http://www.electronics-tutorials.ws]
Amplifiers
Amplifiers
Instrumentation Amplifier Equation
2 R 2 RB
Vout = (V 2 − V 1)[1 +
]( )
R1 RA
Amplifiers
Amplifiers
Precision Instrumentation Amplifier AD524
FEATURES
-Low noise: 0.3 µV p-p at 0.1 Hz to 10 Hz
-Low nonlinearity: 0.003% (G = 1)
-High CMRR: 120 dB (G = 1000) Low offset voltage: 50 µV
-Low offset voltage drift: 0.5 µV/°C
-Gain bandwidth product: 25 MHz
-Pin programmable gains of 1, 10, 100, 1000
-Input protection, power-on/power-off
-No external components required
-Internally compensated
[www.analog.com]
Amplifiers
Amplifiers
Functional block diagram
[www.analog.com]
Amplifiers
Amplifiers
Metallization Photograph Contact factory for latest dimensions;
Dimensions shown in inches and (mm)
[www.analog.com]
Amplifiers
Amplifiers
Indirect Ground Returns for Bias Currents—Thermocouple
[www.analog.com]
Amplifiers
Amplifiers
Typical Bridge Application
[www.analog.com]
Amplifiers
Amplifiers
Single Supply Bridge Transducer Amplifier AD22055
FEATURES:
APPLICATIONS:
-Gain of 400. Alterable from 40 to
1000
Interface for Pressure
Transducers, Position,
Temperature Transducers
-Supply Voltage: +3 V to +36 V
-Peak Input Voltage (40 ms): 60 V
-Reversed Supply Protection: –34 V
Indicator, Strain Gages and Other
Low Level Signal Sources
-Operating Temperature Range: –
40°C to +125°C
[www.analog.com]
Functional block diagram
[www.analog.com]
Typical Application Circuit for a Pressure Sensor Interface
[www.analog.com]
Amplifiers
Amplifiers
LT1101 Precision, Micropower, Single Supply Instrumentation
Amplifier (Fixed Gain = 10 or 100)
APPLICATIONS:
FEATURES:
-Supply Current: 105µA Max
a.Differential Signal Amplification in
Presence of Common Mode Voltage
-Offset Voltage: 160µV Max
b.Micropower Bridge Transducer
Amplifier
-CMRR, G = 100: 100dB Min
– Thermocouples
-Gain Bandwidth Product:
250kHz Min
– Strain Gauges
-Single or Dual Supply Operation
– Thermistors
c.Differential Voltage-to-Current
Converter
d.4mA to 20mA Bridge Transmitter
[www.linear.com]
Amplifiers
Amplifiers
Block diagram
[www.linear.com]
Amplifiers
Amplifiers
Micropower, Battery Operated Remote Temperature Sensor
Trim output to 250mV AT 25°C, Temperature range = 2.5°C TO 150°C, Accuracy =
±0.5°C
[www.linear.com]
Amplifiers
Amplifiers
Voltage Controlled Current
Source
[www.linear.com]
Amplifiers
Amplifiers
Differential Voltage Amplification from a Resistance Bridge
[www.linear.com]
Amplifiers
Amplifiers
INA333 Micro-Power (50mA), Zerø-Drift, Rail-to-Rail Out
Instrumentation Amplifier
FEATURES:
-Low offset voltage: 25mV (max),
-High CMRR: 100dB (min), G ≥ 10,
APPLICATIONS:
Supply range: +1.8V to +5.5V,
-Bridge amplifiers,
Input voltage: (V–) +0.1V to (V+) –
0.1V,
-Pressure sensors,
Output range: (V–) +0.05V to (V+) –
0.05V,
-Thermocouple amplifiers,
Operating temperature: –40°C to
+125°C.
-Medical Instrumentation,
-Data acquisitionn.
[www.ti.com]
Amplifiers
Amplifiers
Block diagram
[www.ti.com]
Amplifiers
Amplifiers
Basic Connections
[www.ti.com]
Amplifiers
Amplifiers
Single-Supply Bridge Amplifier
[www.ti.com]
Oscillators
An electronic oscillator is an electronic circuit that produces a repetitive,
oscillating electronic signal, often a sine wave or a square wave.
[http://en.wikipedia.org/wiki/]
Oscillators
Oscillators
Amplifier
+
Vin+B Vout
A
Vout
Vin
Attenuator B
B Vout
Vout
Basic Oscillator Feedback Circuit
Oscillators
Oscillators
A- open loop voltage gain
B- feedback fraction
A(Vin + BVout ) = Vout
AVin = Vout (1 − AB )
Vout
A
=
Vin 1 − AB
Oscillators are circuits that generate a continuous voltage output
waveform at a required frequency with the values of the inductors,
capacitors or resistors forming a frequency selective LC resonant tank
circuit and feedback network. This feedback network is an attenuation
network which has a gain of less than one ( B <1 ) and starts oscillations
when AB >1 which returns to unity ( AB =1 ) once oscillations
commence.
Oscillators
Oscillators
Types of Oscillators
Sinusoidal Oscillators- generates a purely sinusoidal waveform
which is of constant amplitude and frequency.
Non-Sinusoidal Oscillators- generate complex non-sinusoidal
waveforms as "Square-wave", "Triangular-wave" or "Sawtoothedwave"
RC
RC Oscillators
Oscillators
The RC Oscillator
A single stage amplifier will produce 180O of phase shift between its
output and input signals when connected in a class-A type configuration.
In an RC Oscillator circuit the input is shifted 180O through the amplifier
stage and 180o again through a second inverting stage giving us " 180O
+ 180O = 360O" of phase shift.
In a RC Oscillator, we make use of the fact that a phase shift occurs
between the input to a RC network and the output from the same
network by using RC elements in the feedback branch.
RC
RC Oscillators
Oscillators
C
input
output
R
0
o
60 o
C
C
0
o
R
RC Phase-Shift Network
C
R
R
180o
output
90
O
O
60
input
Single stage
output
O
180
Three stage
Phase shift between the input RC network and the output.
RC
RC Oscillators
Oscillators
1
XC =
2πfC
Z = R + (XC )
2
φ = tan
−1
XC
R
2
RC
RC Oscillators
Oscillators
An amplifier circuit will produce a phase-shift of 180O between its input
and output. If a three-stage RC phase-shift network is connected
between this input and output of the amplifier, the total phase shift
necessary for regenerative feedback will become 3 x 60O + 180O = 360O .
C
0
o
60 o
R
C
120o
R
C 180o
R
AB=1
180 o
RC
RC Oscillators
Oscillators
Vcc
Rl
R1
output
C
0
o
60 o
R
C 120o
R
C 180o
R
Re
Basic RC Oscillator Circuit
RC
RC Oscillators
Oscillators
If all the resistors, R and the capacitors, C in the phase shift network are
equal in value, then the frequency of oscillations produced by the RC
oscillator is given as:
1
fr −
2πRC 2 N
Where:
ƒr- Output Frequency in Hertz
R- Resistance in Ohms
C- Capacitance in Farads
N- number of RC stages (N = 3)
RC
RC Oscillators
Oscillators
Rf
C
60 o
C 120o
C 180o
+
0
o
R
R
A
R
Op-amp RC Oscillator Circuit
output
RC
RC Oscillators
Oscillators
Example
C = 1nF = 1⋅10 −9 F
R = 100kΩ
1
fr =
= 649,75Hz
−9
2 ⋅ π ⋅ 6 ⋅100000 ⋅10
RC
RC Oscillators
Oscillators
The Wien Bridge Oscillator
The Wien Bridge Oscillator is so called because the circuit is based on a
frequency-selective form of the Whetstone bridge circuit.
R1
C1
R2
Vin
R1=R2, C1=C2
RC Phase Shift Network
C2
Vout
RC
RC Oscillators
Oscillators
Vout
1/3 Vin
Output Gain and Phase Shift
φ
fr
Resonance
90o
-90 o
f
fr
Phase Shift
f
RC
RC Oscillators
Oscillators
1
fR =
2πRC
Resonant Frequency
Where:
ƒr is the Resonant Frequency in Hertz
R is the Resistance in Ohms
C is the Capacitance in Farads
RC
RC Oscillators
Oscillators
One part of the feedback
signal is connected to the
inverting input terminal
(negative feedback) via the
resistor divider.
R
C
1/3Vout
+
-
A
V output
C
R
R2
R1
The other part is fed back to
the non-inverting input
terminal (positive feedback)
via the RC Wien Bridge
network
Wien Bridge Oscillator
RC
RC Oscillators
Oscillators
Only at the selected resonant frequency, ( ƒr ) the voltages applied to the
inverting and non-inverting inputs will be equal and "in-phase„.
The positive feedback will cancel out the negative feedback signal
causing the circuit to oscillate.
The voltage gain of the amplifier circuit MUST be equal to three "Gain =
3" for oscillations to start.
Quartz
Quartz Oscillators
Oscillators
The Quartz Crystal Oscillators
One of the most important features of any oscillator is its frequency
stability.
Frequency stability of the output signal can be improved by the proper selection
of the components used for the resonant feedback circuit.
To obtain a very high level of oscillator stability a Quartz Crystal is generally
used as the frequency determining device to produce another types of oscillator
circuit known generally as a Quartz Crystal Oscillator
Quartz
Quartz Oscillators
Oscillators
Vcc
RL
R1
Xt
output
C1
R2
Re
C2
Ce
Colpitts Crystal Oscillator
These types of Crystal Oscillators are designed around the common
emitter amplifier stage of a Colpitts Oscillator.
Electrical
Electrical Waveforms
Waveforms
The Other Electrical Waveforms
Square Wave Waveforms
Square-wave Waveforms are used extensively in electronic and micro
electronic circuits for clock and timing control signals as they are
symmetrical waveforms of equal and square duration representing each
half of a cycle and nearly all digital logic circuits use square wave
waveforms on their input and output gates.
A
Negative Half
Positive Half
t
Period- T
Electrical
Electrical Waveforms
Waveforms
Rectangular Waveforms
Rectangular Waveforms are similar to the square wave waveform above,
the difference being that the two pulse widths of the waveform are of an
unequal time period. Rectangular waveforms are therefore classed as
"Non-symmetrical" waveforms.
A
Negative Half
Positive Half
t
Period- T
Electrical
Electrical Waveforms
Waveforms
Triangular Waveforms
Triangular Waveforms are generally bi-directional non-sinusoidal
waveforms that oscillate between a positive and a negative peak value.
A
t
Period- T
Electrical
Electrical Waveforms
Waveforms
Sawtooth Waveforms
Sawtooth Waveforms are another type of periodic waveform. As its
name suggests, the shape of the waveform resembles the teeth of a saw
blade.
A
t
Period- T
Electrical
Electrical Waveforms
Waveforms
Function Generator
A Function Generator or sometimes called a Waveform Generator is a
device or circuit that produces a variety of different waveforms at a
desired frequency. It can generate Sine waves, Square waves,
Triangular and Sawtooth waveforms as well as other types of output
waveforms
IC
IC Electrical
Electrical Waveforms
Waveforms
ICL8038- Precision Waveform Generator/Voltage
Controlled Oscillator
Functional Diagram
[http://www.intersil.com/]
IC
IC Electrical
Electrical Waveforms
Waveforms
Detailed Schematic
[http://www.intersil.com/]
IC
IC Electrical
Electrical Waveforms
Waveforms
Parameters:
-Low Frequency Drif with Temperature
-Low Distirtion- 1% (Sine Wave Output)
-High Linearity- 0,1%
-Wide Frequency Range- 0,001Hz-300kHz
-High Level Outputs- TTL to 28V
-Easy to use
[http://www.intersil.com/]
IC
IC Electrical
Electrical Waveforms
Waveforms
Waveform Generator IC
[http://www.electronics-tutorials.ws]
IC
IC Electrical
Electrical Waveforms
Waveforms
AD5932 Programmable Frequency Scan Waveform Generator
Parameters:
-Programmable Frequency Scan
-No external components necessary
-Output frequency up to 25 MHz
-Power supply: 2.3 V to 5.5 V
-Automotive temperature range: −40°C to +125°C
[http://www.analog.com/]
IC
IC Electrical
Electrical Waveforms
Waveforms
Functional Block Diagram
[http://www.analog.com/]
IC
IC Electrical
Electrical Waveforms
Waveforms
80C51/80L51 to AD5932 Interface
[http://www.analog.com/]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
Voltage-Controlled Oscillator (VCO)
Voltage Controlled Current
Source
Vin
C
+
-
Vout
Comparator
Vref
Reset
VCO- Block diagram
[http://sequence15.blogspot.com/2008/02/how-vco-works.html]
VCO
VCO
Voltage Controlled Current
Source
Vin
C
+
-
Vout
Comparator
Vref
Reset
If a constant current is applied to the capacitor, the voltage across the capacitor
will rise at a constant rate.
A fairly basic circuit can take the control voltage and output a constant current
which is proportional to the voltage.
While capacitor is charging, a voltage comparator constantly compares the
voltage across the capacitor to a reference voltage.
When the voltage across the cap exceeds the reference voltage, the comparator
momentarily triggers the transistor which shorts out the cap, discharging it back
to the starting voltage.
VCO
VCO
LM566C Voltage Controlled Oscillator
Connection Diagram
[www.national.com]
VCO
VCO
Typical Application
1 kHz and 10 kHz TTL Compatible Voltage Controlled Oscillator
[www.national.com]
VCO
VCO
2,4(V + − V 5)
fO =
RO CO
where
2k < RO < 20k
Features
V5- voltage between pin 5 i pin 1
Applications
-Wide supply voltage range: 10V to
24V
-FM modulation
-Very linear modulation characteristics
-Function generation
-High temperature stability
-Frequency shift keying
-Frequency programmable by means of
current, voltage, resistor or capacitor
-Tone generation
-Signal generation
[www.national.com]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
LM231A/LM231/LM331A/LM331 Precision Voltage-toFrequency Converters
The LM231/LM331 family of voltage-to-frequency converters are ideally
suited for use in simple low-cost circuits for analog-to-digital conversion,
precision frequency-to-voltage conversion.
Parameters:
-Operates on Single 5V Supply
-Pulse Output Compatible with All Logic Forms pulse
-Low Power Consumption: 15 mW Typical at 5V
-Wide Range of Full Scale Frequency: 1 Hz to 100 kHz
-Low Cost
[www.ti.com]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
Functional Block Diagram
[www.ti.com]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
Simplified Block Diagram of Stand-Alone Voltage-to-Frequency
Converter and External Components
[www.ti.com]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
The voltage comparator compares a positive input voltage, V1, at pin 7
to the voltage, Vx, at pin 6. If V1 is greater, the comparator will trigger
the 1-shot timer. The output of the timer will turn ON both the frequency
output transistor and the switched current source for a period t=1.1 RtCt.
During this period, the current i will flow out of the switched current
source and provide a fixed amount of charge, Q = i × t, into the
capacitor, CL. This will normally charge Vx up to a higher level than V1.
At the end of the timing period, the current will turn OFF, and the timer
will reset itself.
[www.ti.com]
Voltage
-to-Frequency Converter
s
Voltage-to-Frequency
Converters
Simple Stand-Alone V-to-F Converter with ±0.03% Typical Linearity (f =
[www.ti.com]
10 Hz to 11 kHz)
Bibliogaphy:
http://www.electronics-tutorials.ws/
www.ti.com
www.analog.com
http://www.electronicshub.org/