Opamp Negative Feedback
Negative Feedback
The use of negative feedback reduces the gain, but most other rationales favor its use. Part of the output signal is taken back to the input with a negative sign.
For an amplifer with negative feedback the gain becomes
The large open loop gain of an op-amp makes it possible to build amplifiers whose gain is determined by the feedback B and not by the gain of the amplifying element itself!
Why use negative feedback?
Rationale for Negative Feedback
Why would you feed back a negative signal from the output which cancels part of the input, reducing the gain?
Because:
- It helps to overcome distortion and nonlinearity.
- It flattens frequency response or allows you to tailor it to a desired frequency response curve.
- It makes properties predictable, less dependent on temperature, manufacturing differences or other internal properties of the active device.
- Circuit properties are dependent upon the external feedback network and are thus easily controlled by external circuit elements.
- Circuit design can concentrate on function and not the details of operating point selection, biasing, and the other details characteristic of discrete transistor amplifier design.
Keywords :
Opamp,
Op-amp,
negative,
Feedback,
Amplifier,
Differentiation
Writer : delon |
13 Mar 2006 Mon
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