AmplifiersAmplifiersAmplifiers
An electronic amplifier , amplifier , or amp - is an electronic device that increases the power of a signal .
[http:// en .wikipedia .org /wiki /] AAA WheatstoneWheatstoneWheatstone bridgebridgebridge 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 CD 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. AAA WheatstoneWheatstoneWheatstone bridgebridgebridge At the point of balance , the ratio of :
R2 = 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+ R2 BBBridgeridgeridge CC Circuitsircuitsircuits Resistive elements are some of the most common sensors . Sensor elements' resistances can range from less than 100 Ω to several hundred kΩ, depending on the sensor design and the physical environment to be measured . Resistance of popular sensors : -Strain Gages (czujniki nap ręż enia ) 120 Ω , 350 Ω , 3500 Ω -Pressure Sensors (czujniki ci śnienia) 350 Ω - 3500 Ω -Relative Humidity (czujniki wigotno ści ) 100k Ω - 10M Ω -Resistance Temperature Devices (czujniki temperatury) 100 Ω , 1000 Ω -Thermistors (termistory) 100 Ω - 10M Ω
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The basic Wheatstone bridge [www .analog. com ] BBBridgeridgeridge CC Circuitsircuitsircuits 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 ] AmplifiersAmplifiersAmplifiers
R R Vcc - Vout K + R 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 ] AmplifiersAmplifiersAmplifiers
Vcc t Relay Thermistor R1Vcc Rf D - V- K V+ + R3 P R2 Adjust
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. AmplifiersAmplifiersAmplifiers
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.
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V1 + K1 - RB R2 RA Va - R1 K3 R2 RA + Vout Vb - K2 RB + V2
High Input Impedance Instrumentation Amplifier
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Instrumentation Amplifier Equation
2R2 RB Vout = (V 2 −V )[1 1+ ]( ) R1 RA AmplifiersAmplifiersAmplifiers
Precision Instrumentation Amplifier AD524 FEATURES -Low noise: 0.3 V 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 V -Low offset voltage drift: 0.5 V/°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 ] AmplifiersAmplifiersAmplifiers
Functional block diagram
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Metallization Photograph Contact factory for latest dimensions ; Dimensions shown in inches and (mm)
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Indirect Ground Returns for Bias Currents —Thermocouple
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Typical Bridge Application
[www .analog. com ] AmplifiersAmplifiersAmplifiers Single Supply Bridge Transducer Amplifier AD22055
FEATURES : APPLICATIONS : -Gain of 400. Alterable from 40 to Interface for Pressure 1000 Transducers, Position, -Supply Voltage: +3 V to +36 V Temperature Transducers -Peak Input Voltage (40 ms): 60 V Indicator, Strain Gages and Other Low Level Signal Sources -Reversed Supply Protection: –34 V -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 ] AmplifiersAmplifiersAmplifiers LT1101 Precision , Micropower , Single Supply Instrumentation Amplifier (Fixed Gain = 10 or 100) APPLICATIONS : FEATURES: a. Differential Signal Amplification in Presence of Common Mode Voltage -Supply Current : 105 A Max b. Micropower Bridge Transducer -Offset Voltage : 160 V Max Amplifier -CMRR, G = 100: 100dB Min -CMRR, G = 100: 100dB Min – Thermocouples -Gain Bandwidth Product : -Gain Bandwidth Product : – Strain Gauges 250kHz Min – Thermistors -Single or Dual Supply Operation c. Differential Voltage -to -Current Converter d.4mA to 20mA Bridge Transmitter [www .linear .com ] AmplifiersAmplifiersAmplifiers
Block diagram
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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 ] AmplifiersAmplifiersAmplifiers
Voltage Controlled Current Source
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Differential Voltage Amplification from a Resistance Bridge
[www .linear .com ] AmplifiersAmplifiersAmplifiers INA333 Micro -Power (50mA), Zer ø-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+) – -Pressure sensors , 0.1V , -Medical Instrumentation , Output range : (V –) +0.05V to (V+) – -Thermocouple amplifiers , 0.05V , -Data acquisitionn . Operating temperature : –40 °C to +125 °C.
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Block diagram [www .ti .com ] AmplifiersAmplifiersAmplifiers
Basic Connections
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Single -Supply Bridge Amplifier
[www .ti .com ] OscillatorsOscillatorsOscillators 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 /] OscillatorsOscillatorsOscillators
Amplifier Vin+B Vout + A
Vin Vout
Attenuator B B Vout Vout
Basic Oscillator Feedback Circuit OscillatorsOscillatorsOscillators
A- open loop voltage gain B- feedback fraction A(Vin + BVout ) = Vout AVin = Vout 1( − AB ) Vout = A Vin 1− AB Oscillator s 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 ( A B =1 ) once oscillations commence . OscillatorsOscillatorsOscillators
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 "Sawtoothed - wave " RCRCRC OscillatorsOscillatorsOscillators
The RC Oscillator A single stage amplifier will produce 180 O 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 180 O through the amplifier stage and 180o again through a second inverting stage giving us " 180 O + 180 O = 360 O" 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 . RCRCRC OscillatorsOscillatorsOscillators
inputC output C C C
R R R R o o o 0 o 0 60 180
RC Phase -Shift Network output
O 90 Single stage O 60 input output
O 180 Three stage
Phase shift between the input RC network and the output . RCRCRC OscillatorsOscillatorsOscillators 1 X = C 2πfC = 2 + 2 Z R (X C )
− X φ = tan 1 C R RCRCRC OscillatorsOscillatorsOscillators
An amplifier circuit will produce a phase -shift of 180 O 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 + 180 O = 360 O .
o o o C 60 C 120 C 180 AB=1 180 o
R R R o 0 RCRC OscillatorsOscillators RC Oscillators Vcc
R1 Rl output
C 60 o C 120 o C 180 o
R R R o Re 0
Basic RC Oscillator Circuit RCRCRC OscillatorsOscillatorsOscillators
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 f − r 2πRC 2N
Where : ƒr Output Frequency in Hertz R Resistance in Ohms C Capacitance in Farads N number of RC stages (N = 3) RCRCRC OscillatorsOscillatorsOscillators
Rf
C 60 o C 120 o C 180 o - A + R R R output o 0
Op -amp RC Oscillator Circuit RCRCRC OscillatorsOscillatorsOscillators
Example
C =1nF =1⋅10 −9 F R =100 kΩ 1 fr = = 649 75, Hz 2⋅π ⋅ 6 ⋅100000 ⋅10 −9 RCRCRC OscillatorsOscillatorsOscillators
The Wien Bridge Oscillator The Wien Bridge Oscillator is so called because the circuit is b ased on a frequency -selective form of the Whetstone bridge circuit . R1 C1
Vin R2 C2 Vout
R1=R2, C1=C2
RC Phase Shift Network RCRCRC OscillatorsOscillatorsOscillators Vout
1/3 Vin
Output Gain and Phase Shift
φ f fr Resonance 90 o
f f -90 o r Phase Shift RCRCRC OscillatorsOscillatorsOscillators 1 f = R 2πRC
Resonant Frequency
Where : ƒr is the Resonant Frequency in Hertz R is the Resistance in Ohms C is the Capacitance in Farads RCRCRC OscillatorsOscillatorsOscillators
One part of the feedback signal is connected to the R inverting input terminal (negative feedback ) via the C 1/3Vout resistor divider . + A - The other part is fed back to V output C the non -inverting input R terminal ( positive feedback ) R1 via the RC Wien Bridge R2 network
Wien Bridge Oscillator RCRCRC OscillatorsOscillatorsOscillators
Only a t 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 . QuartzQuartzQuartzOscillatorsOscillators 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 QuartzQuartzQuartzOscillatorsOscillators Oscillators Vcc
RL R1 Xt
output
C1 C2 R2 Re Ce
Colpitts Crystal Oscillator These types of Crystal Oscillators are designed around the commo n emitter amplifier stage of a Colpitts Oscillator . ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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 ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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 ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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 ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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 ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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 ICICIC ElectricalElectricalElectrical WaveformsWaveformsWaveforms ICL8038 - Precision Waveform Generator/ Voltage Controlled Oscillator
Functional Diagram [http:// www .intersil .com /] ICICIC ElectricalElectricalElectrical WaveformsWaveformsWaveforms
Detailed Schematic [http:// www .intersil .com /] ICICIC ElectricalElectricalElectrical WaveformsWaveformsWaveforms
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
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Waveform Generator IC
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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
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Functional Block Diagram
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80C51/80L51 to AD5932 Interface
[http:// www .analog. com /] VoltageVoltageVoltage-to-Frequency--toto --FrequencyFrequency ConverterConverterConvertersss 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 ] VCOVCOVCO 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 . VCOVCOVCO LM566C Voltage Controlled Oscillator
Connection Diagram
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Typical Application 1 kHz and 10 kHz TTL Compatible Voltage Controlled Oscillator [www .national .com ] VCOVCOVCO + − = (4,2 V V )5 fO ROCO where < < 2k RO 20 k V5 - voltage between pin 5 i pin 1 Features Applications -Wide supply voltage range : 10V to FM modulation 24V Signal generation -Very linear modulation characteristics Function generation -High temperature stability Frequency shift keying -Frequency programmable by means of Tone generation current , voltage , resistor or capacitor [www .national .com ] VoltageVoltageVoltage-to-Frequency--toto --FrequencyFrequency ConverterConverterConvertersss
LM231A/LM231/LM331A/LM331 Precision Voltage -to - Frequency 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 ] VoltageVoltageVoltage-to-Frequency--toto --FrequencyFrequency ConverterConverterConvertersss
Functional Block Diagram [www .ti .com ] VoltageVoltageVoltage-to-Frequency--toto --FrequencyFrequency ConverterConverterConvertersss
Simplified Block Diagram of Stand -Alone Voltage -to -Frequency Converter and External Components
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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.
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Simple Stand -Alone V-to -F Converter with ±0.03% Typical Linearity (f = 10 Hz to 11 kHz ) [www .ti .com ] Bibliogaphy: http://www.electronics-tutorials.ws/ www.ti.com www.analog.com http://www.electronicshub.org/