Electronic Devices and Circuits Engineering Sciences 154

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. Bandwidth Extension:
 
(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
 
 
3. Distortion Reduction:
 
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