"One week to solve the model electricity" - negative feedback

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One 、 What is feedback ？

The concept of feedback also appears in the principle of automatic control , Is a very important concept in control .
feedback ： The output signal and input signal of the system are superimposed and input to the system
Feedback is divided into positive feedback and negative feedback .
Next , Let's focus on negative feedback ：

Deep negative feedback , The magnification is mainly determined by the feedback coefficient .

Two 、 Negative feedback

Stable static operating point ; Stable magnification ; Improve input and output resistance ; Broaden the passband , Improve output signal waveform .

3、 ... and 、 Positive feedback

AF The absolute value of is 1 when , The amplification amount is inversely related to the feedback amount , The circuit generates self excitation , No signal source can also produce signal output .
When AF>1, The magnification is too large , The output signal keeps increasing , Do not limit in time , The signal will be seriously distorted .
AF<1, Too much feedback , The signal is decaying , Until it disappears .