The document discusses various types of amplifiers and signal processing circuits. It begins by explaining the need for signal amplification and conditioning when transducer outputs are too small, noisy, or contain unwanted information. It then describes the basic operation of amplifiers, including voltage gain, input and output impedance. The rest of the document discusses operational amplifiers and various circuits that can be created using op amps, including inverting and non-inverting amplifiers, summers, integrators, differentiators, comparators, and more. It also covers analog to digital conversion techniques like sampling, quantization, successive approximation, and flash converters.

1. AmplifiersAmplifiersAmplifiersAmplifiers

2. AmplifiersAmplifiers
Introduction
Transducer output is an analog signal that is not always in the required form.
They may:
•Be too small, (mV);
•Be too noisy, (due to electromagnetic interference)
•Contain the wrong information,
•Have a DC offset,
•Many of these problems can be remedied, through appropriate analog
signal processing
•Most common forms of signal processing:
•Amplification (the simplest one); signal inversion; differentiation; integration;
addition; subtraction; and comparison

3. AmplifiersAmplifiers
Goal
Design simple amplifiers using
integrated circuits
When choosing or designing an
amplifier we must consider:
size, cost, power, input impedance,
output, impedance, gain, and bandwidth;
Amplifier model: 2-port device
Voltage gain: Av = Vout/Vin;
Zin = Vin/Iin;
Zout = Vout/Iout;

4. Operational AmplifiersOperational Amplifiers
• Op Amp is a low cost and versatile IC consisting of may internal transistors,
resistors, and capacitors manufactured into a single chip;
• The op amp is the basic building block for:
• amplifiers; integrators; summers; differentiators;
• comparators; A/D and D/A converters; active filters; sample and hold
amplifiers;

5. Ideal Model for the Op AmpIdeal Model for the Op Amp
• Op amp is an active device with
differential input, single output
amplifier that is assumed to have
infinite gain
Ideal model assumptions:
• infinite impedance at both inputs
• infinite gain has zero output
impedance

6. 741 Op Amp Integrated Circuit741 Op Amp Integrated Circuit

7. Inverting Amplifier
• The circuit inverts and amplifies the input
voltage
• Resistor RF forms the feedback loop
• Applying Kirchhoff’s current law at node C
and utilizing assumption 1 (no current flows
into the inputs
• iin = -iout; also VC = 0Input output
relationship for the inverting ampl.
• Vout/Vin = - RF/R

8. Non-inverting AmplifierNon-inverting Amplifier
• The circuit amplifies the input
voltage without inverting the
signal
We have VC = Vin
iout = (Vout – Vin)/RF
The gain is: Vout/Vin = 1 + RF/R
The noninverting amplifier has a
positive gain Buffer or follower
circuit:
• has a high input impedance and
low output impedance

9. Summer CircuitSummer Circuit
• Used to add analog signals
• R1 = R2 = RF
• Vout = - (V1+V2)

10. Difference Amplifier
• Difference amplifier circuit
• Analyze the circuit based on
• the superposition principle

11. Instrumentation AmplifierInstrumentation Amplifier
ICs:ICs:
•Analog Devices 524 and 624, National
Semiconductor
•LM 623
•A single external resistor is used to set the gain higher
and more stable than gains achievable with a simple
difference amplifier
Characteristics:Characteristics:
•very high input impedance;
•Large common mode rejection ration (CMMR)
•CMMR is the ration of the difference mode gain to
the common mode gain
•Capability to amplify low-level signals in a noisy
environment
•Consistent bandwidth over a large range of gains
Circuit with discrete op amps and
precision resistors

12. • The output signal is an inverted,
scaled integral of the input
signal
• Vout(t) = …
• A practical integrator circuit
includes a shunt resistor Rs
• the purpose of Rs is to limit low-
frequency gain of the circuit.

13. DifferentiatorDifferentiator
• The output signal is an inverted, scale derivative of
• the input signal
• Vout = …
• Differentiation is a signal processing method that
• tends to accentuate the effects of noise whereas
• integration smoothens signals over time

14. Logarithmic AmplifierLogarithmic Amplifier
• A signal conditioner might be used to
linearize the output of sensors that are
non-linear
• This is done by a suitable choice of
component for the feedback circuit
of an operational amplifier
• Logarithmic amplifier output
• Vout = …

15. Sample and Hold CircuitSample and Hold Circuit
• Used in A/D converters
• signal must be stabilized while it is
converted. The sample and hold circuit
consists of a voltage-holding capacitor
and a voltage follower
S closed:
• Vout(t) = Vin(t)
• S open:
• Vout(t-tsampled) = Vin(tsampled)

16. ComparatorComparator
• Is used to determine if one signal is
greater then another
• Comparator has no negative
feedback result is that the op amp
saturates Vout = …
• Some comparators (LM339) have
open collector outputs

17. The Real Op AmpThe Real Op Amp
• Have a very high input impedance
• There is very little voltage difference between the
input terminals
• The maximum voltage output is less then V supply
The response to a step input is characterized by 2
parameters:
• slew rate …
• rise time …
• Frequency response has a finite bandwidth
• gain bandwidth product (GBP) = …

18. Important Parameters from Op Amp Data SheetsImportant Parameters from Op Amp Data Sheets
Input Parameters
•Input voltage: Vicm
•input offset voltage: Vio
•Input bias current: Iib
•input offset current: Iio
•input voltage range: Vcm
•Input resistance: Zi
•Output parameters
•output resistance: Zoi
•output short circuit
•current: Iosc
•Output voltage swing
Dynamic parameters
•open loop voltage gain
•Aol
•large signal voltage gain
•Slew rate: SR
•Other parameters
•Max supply voltage:
•Supply current:
•common mode rejection
•ration: CMRR
•Channel separation:

19. Example of Sizing the Op Amp CircuitsExample of Sizing the Op Amp Circuits
• The ideal model of the op amp would imply that both these circuits have
same gain of -2
• However the top circuit would be a very poor design

20. Examples of Circuits with Op AmpsExamples of Circuits with Op Amps
Example 1: differential amplifier application:
•530uV emf, for a 10 C temperature difference between
•the thermocouple junctions; For V out = 10 mV, R1, R2 =?
Example 2: temperature switch application
•when a critical temperature is reached a relay is activated
Example 3: same thermocouple circuit
•copper-constantan with sensitivity of 43 uV/C
•for 100 C difference, V out = 10 mV. R1, R2 = ?

21. Sampling TheoremSampling Theorem
• fs > 2fmax; where fs is the sampling
frequency and f max is the highest
frequency component in the input
analog signal;
• 2fmax – Ny quist frequency
• Δt = 1/ fs
• If fs < 2fmax
• aliasing can result

22. Quantizing TheoryQuantizing Theory
A/D conversion:
•Step 1: Quantizing
•Step 2: Coding
•Resolution of A/D is the number of bits
used to approximate the signal
•commercial A/Ds: 8-, 10-, or 12- bits
•Number of analog decision points = N-1
•The analog quantization size Q = …
Result of sampling of a linear ramp of an
analog signal

23. A/D ConversionA/D Conversion
To properly acquire an analog voltage signal for digital processing,
the following components must be properly selected and applied in
this sequence:
•Buffer amplifier …
•Low-pass filter …
•Sample and hold amplifier …
•A/D converter …
•Computer …

24. Successive Approximation A/D ConverterSuccessive Approximation A/D Converter
• Uses a D/A
• converter in the feedback loop
• If n is the resolution of the A/D, it
takes n steps to complete the
conversion
• Process: start by setting msb to 1
• Example

25. A/D Flash Back ConverterA/D Flash Back Converter
• Fastest A/D
• Consist of a bank of input
comparators acting in parallel
• Example: 2-bit converter
• resolution: 4 states
• input range: Vmin = 0;
• Vmax = 4 V

26. D/A ConversionD/A Conversion
• The simplest D/A is a resistor ladder network
connected to an op amp
Example: 4-bit, R-2R resistor ladder network
• it requires only 2 precision resistance values (R
and 2R)
• Vout = b3Vout3 + b2Vout2 + b1Vout1 + b0Vout0

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