Amplifier Circuit

Amplifier Circuit

1. Negative feedback

   • When the feedback energy (voltage or current) is out of phase with the input signal and thus opposes it.
   • • The result is that the feedback voltage Vf is 180° out of phase with the input signal Vin.

2. Effects on the voltage gain

   • Reduces non-linear distortion
     • • It is clear that by applying negative voltage feedback to an amplifier, distortion is reduced by a factor 1 + Av mv
   • Improves frequency response
     • The result is that voltage gain of the amplifier will be substantially constant over a wide range of signal frequency.
       • The negative voltage feedback, therefore, improves the frequency response of the amplifier.
   • Gain stability. Can be made independent of transistor parameters or the supply voltage variations.
   • Increases circuit stability
   • Increases input impedance and decreases output impedance
     • The negative voltage feedback increases the input impedance and decreases the output impedance of amplifier.
     • Input impedance
     • Output impedance

3. Non-inverting

   • The calculation hinges around the fact that the voltage at both inputs is the same. This arises from the fact that the gain of the amplifier is exceedingly high.
     • If the output of the circuit remains within the supply rails of the amplifier, then the output voltage divided by the gain means that there is virtually no difference between the two inputs.

4. Inverting

   • Operational amplifier is connected with feedback to produce a closed loop operation.
     • • No current flows into the input terminals and the differential input voltage is zero as v1 = v2 = 0

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