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Chapter: Electronic Circuits - Feed Back Amplifiers

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Principles of Negative Current Feedback

In this method, a fraction of output current is fedback to the input of the amplifier.

Principles of Negative Current Feedback

 

In this method, a fraction of output current is feedback to the input of the amplifier. In other words, the feedback current (If) is proportional to the output current (Iout) of the amplifier. Fig. 1.7 shows the principles of negative current feedback. This circuit is called current-shunt feedback circuit. A feedback resistor Rf is connected between input and output of the amplifier. This amplifier has a current gain of Ai without feedback. It means that a current I1 at the input terminals of the amplifier will appear as Ai I1 in the output circuit i.e., Iout = Ai I1.

 

Now a fraction mi of this output current is fedback to the input through Rf. The fact that arrowhead shows the feed current being fed forward is because it is negative feedback.


Note that negative current feedback reduces the input current to the amplifier and hence its current gain.

 

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