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    Chapter 10

    Uploaded by

    Nasser Almofari
    Operational amplifiers, or op-amps, are high-gain differential amplifiers with two input terminals (inverting and non-inverting) and one output terminal. Op-amps have very high open-loop gain but this is reduced when used in a closed-loop configuration with negative feedback. Common op-amp circuits include the inverting amplifier, non-inverting amplifier, unity follower, summing amplifier, integrator, and differentiator. Each circuit configuration results in a different transfer function between the input and output terminals.

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    © All Rights Reserved
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    Chapter 10

    Uploaded by

    Nasser Almofari
    62 views18 pages
    Operational amplifiers, or op-amps, are high-gain differential amplifiers with two input terminals (inverting and non-inverting) and one output terminal. Op-amps have very high open-loop gain but this is reduced when used in a closed-loop configuration with negative feedback. Common op-amp circuits include the inverting amplifier, non-inverting amplifier, unity follower, summing amplifier, integrator, and differentiator. Each circuit configuration results in a different transfer function between the input and output terminals.

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    chapter 10

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    Operational amplifiers, or op-amps, are high-gain differential amplifiers with two input terminals (inverting and non-inverting) and one output terminal. Op-amps have very high open-loop gain but this is reduced when used in a closed-loop configuration with negative feedback. Common op-amp circuits include the inverting amplifier, non-inverting amplifier, unity follower, summing amplifier, integrator, and differentiator. Each circuit configuration results in a different transfer function between the input and output terminals.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    62 views18 pages

    Chapter 10

    Uploaded by

    Nasser Almofari
    Operational amplifiers, or op-amps, are high-gain differential amplifiers with two input terminals (inverting and non-inverting) and one output terminal. Op-amps have very high open-loop gain but this is reduced when used in a closed-loop configuration with negative feedback. Common op-amp circuits include the inverting amplifier, non-inverting amplifier, unity follower, summing amplifier, integrator, and differentiator. Each circuit configuration results in a different transfer function between the input and output terminals.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    of 18

    Chapter 10

    Operational Amplifier

    1
    Basic Op-Amp

    Operational amplifier or op-amp, is a very high gain


    differential amplifier with a high input impedance (typically a
    few meg- Ohms) and low output impedance (less than 100 ).

    Note the op-amp has two inputs and one output.

    2
    Basic Op-Amp
    Symbol

    • One of the input terminals (1) is called an inverting


    input terminal denoted by ‘-’
    • The other input terminal (2) is called a non-inverting
    input terminal denoted by ‘+’
    3
    Op-Amp

    +
    V o Non-inverting
    ~ Vi • + terminal : Source
     • – terminal : Ground
    • 0o phase change

    +
    V o
    Inverting
    • + terminal : Ground
     • – terminal : Source
    ~
    V i
    • 180o phase change

    4
    Basic Amp.

    5
    IC Product

    6
    Vin(+) Vin(-) IC Product
    V+

    Vo

    V
    -

    Internal circuitry of LM741.

    7
    Common-Mode Operation

    • Ideally, the two inputs are equally amplified, and since they
    result in opposite-polarity signals at the output, these signals
    cancel, resulting in 0-V output.
    • Practically, a small output signal will result.
    8
    Common-Mode Rejection
    • A significant feature of a differential connection is that:
    • The signals that are opposite at the inputs are highly
    amplified,
    • Signals that are common to the two inputs are only
    slightly amplified
    • The overall operation being to amplify the difference
    signal while rejecting the common signal at the two
    inputs.
    • Since noise (any unwanted input signal) is generally
    common to both inputs, it canceled.
    • This operating feature is referred to as common-mode
    rejection .
    9
    Op-Amp Gain
    Op-Amps have a very high gain. They can be connected
    open- loop or closed-loop.

    • Open-loop refers to a configuration where there is no


    feedback from output back to the input. In the open-
    loop configuration the gain can exceed 10,000.

    • Closed-loop configuration reduces the gain. In order to


    control the gain of an op-amp it must have feedback.
    This feedback is a negative feedback. A negative
    feedback reduces the gain and improves many
    characteristics of the op-amp.

    10
    Inverting Op-Amp

    • The signal input is applied to the inverting (–) input


    • The non-inverting input (+) is grounded
    • The resistor Rf is the feedback resistor. It is connected from
    the output to the negative (inverting) input. This is
    negative feedback.
    11
    Inverting Op-Amp Gain
    Gain can be determined from external resistors: Rf and R1

    A v  Vo  R f
    Vi R1

    Unity gain—voltage gain is 1

    Rf  R1
     R f  1
    Av 
    R1

    The negative sign denotes a 180 phase


    shift between input and output.

    12
    AC equivalent of op-amp circuit
    Practical Op-Amp Circuits

    Inverting amplifier
    Noninverting amplifier
    Unity follower
    Summing amplifier
    Integrator
    Differentiator

    13
    Inverting/Noninverting Op-Amps
    Inverting Noninverting Amplifier
    Amplifier
     Rf Rf
    Vo  V1 Vo  (1  )V1
    R1 R1

    14
    Unity Follower

    V o  V1

    15
    Summing
    Amplifier

    R R 


    Vo   fR f f
    V  V  V 
     R1 1 R 2 2 R 3 3 

    16
    Integrator

    •The output is the


    integral of the input.
    •This circuit is useful in
    low-pass filter circuits.

    1
    v o (t)   RC v 1 (t)dt
    17
    Differentiator

    •The differentiator
    takes the derivative
    of the input.
    •This circuit is useful
    in high-pass filter
    circuits.

    dv 1 (t)
    v o (t)  RC dt

    18

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