A quick theory on Amplifiers

Amplifier’s job is to increase the output gain which is measured in the dB scale.
dB scale reference

dB value equivalent multification factor
+30 dB 1000
+20 dB 100
+16 dB 40
+13 dB 20
+10 dB 10
+9 dB 8
+8 dB 6.31
+7 dB 5.01
+6 dB 4
+5 dB 3.16
+4 dB 2.51
+3 dB 2
+2 dB 1.58
+1 dB 1.26
0 dB 1
-3 dB 0.5
-10 dB 0.1
-20 dB 0.01
-30 dB 0.001
-40 dB 0.0001

Feedback amplifiers are designed such that a smaller fraction of its output signal is fed back to the input. There are two ways of feedback implementation, positive feedback and Negative feedback.

feedback amplifier image

Positive Feedback Amplifiers: Fraction of output signal is added to the input signal and then sent to the amplifier.When the input signal strength is very low and if we want to increase its strength, we go for a carefully designed positive feedback amplifier. Positive feedback amplifier are highly prone to oscillations. Thus it ‘ll be deployed in a very controlled environment.

Negative Feedback Amplifiers: Fraction of output signal is fed back to the inverting input of the amplifier. For easier understanding it can be taken as subtraction of the input to the output. This is used to improve the gain stability.



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