G Design single input op-amp circuits with with closed loop gains of −10, +10, +1 and −1. Use 10kΩ for the feedback resistor Rf in your designs. What type of feedback is used in the ±10 gain amplifiers? Explain with appropriate equations the effect of feedback on input and output resistances of the amplifier circuits.

Explanation:

For Gain of −10

Inverting op-amp gain is given by

The negative sign represents output signal being phase shifted by 180°

Ω  

For Gain of −1

Ω

For Gain of +10

Non-inverting op-amp gain is given by

Ω

For Gain of +1

To get a Gain of +1, make  which results in ∞

The output is directly connected to the input which makes equal to Therefore, giving a gain of exactly 1.

This kind of design configuration is also known as Voltage Follower.

Negative feedback is being used to design these op-amp amplifiers.

Negative feedback increases the stability at the cost of reduced gain.

The gain is reduced by a factor of  

Negative feedback reduces noise and distortion and improves frequency response of the amplifier.

An ideal op-amp should have infinite input resistance and zero output resistance. Negative feedback increases the input impedance and reduces the output impedance.