Electronic Devices and Circuits
Engineering Sciences 154

Amplifier Characteristics


Amplifier Symbols

Amplifier Equivalent Circuit
Miscellaneous amplifier references:
  • The quest for the ideal rf amplifier
  • Examples of high performance rf amplifier 
  • Amplifier Basics
  • The importance of input and output impedance:



    Therefore, in most instances, we require than

    and 

    or we can say that high input impedance and low output is a desirable quality in most amplifiers!

    Typical Frequency Response:

    Amplifier Distortion:

    Feedback in Amplifier Circuits:


      Notice that



       
       
       

      What's so great about feedback?

    1. Gain Desensitivity:

    2.  

       
       



    3. Bandwidth Extension:
      1.  
        (see Decibel Measure and Asymptotic Bode Plots and Decibel Measure and Asymptotic Bode Plots for two nice Bode plot references)
         
        Suppose
          - See corresponding Bode plot
        With feedback
      s
         
        so that with feedback - See corresponding Bode plot
         
         
    4. Distortion Reduction:
      1.  
        If you were to put the nonlinear input/output response (gain curve) illustrated above into the closed-loop gain expression, you would find:


    Operational Amplifiers - Op Amps:

    For a valuable reference on op amps see the Texas Instruments "White paper"  Understanding Operational Amplifier Specifications by Jim Karki

    Another two nice references on op amps can seen at Operational Amplifiers (source) and at Op Amp Basics  (Also see Bowden's Hobby Circuits)

    A discussion of Op Amp Filter Circuits


    This page was prepared and is maintained by R. Victor Jones
    Comments to: jones@seas.harvard.edu.

    Last updated April 23,  2010