The document discusses an inverting amplifier, which uses an operational amplifier to amplify an input signal but inverts the phase of the output signal. An inverting amplifier applies a positive input voltage but produces a negative output voltage. It has a high gain that is determined by the ratio of the feedback resistance to the input resistance. The input is connected to the inverting terminal through a resistor R, while negative feedback is provided through a resistor Rf between the output and inverting input. This configuration produces an output signal that is 180 degrees out of phase with the input.

1. Inverting Amplifier
Dr.R.Hepzi Pramila Devamani,
Assistant Professor of Physics,
V.V.Vanniaperumal College for Women,
Virudhunagar

2. Operational Amplifier:
An operational amplifier (Op-Amp)is an integrated circuit
that uses external voltage to amplify the input through a very
high gain.

3. Applications:
• Inverting Amplifier
• Non-inverting Amplifier
• Summing amplifier
• Subtracting Amplifier
• Integrator
• Differentiator

4. Inverting amplifier:
Definition:
Inverting amplifier is one in which the output is exactly 180 degree
out of phase with respect to input.Output is an inverted amplified
version of input.If we apply a positive voltage,output will be
negative.

5. Circuit Diagram:

6. Circuit Operation:
• A voltage source Vs (a.c or d.c) is connected to the inverting
terminal of the op-amp through the resistance R.
• A negative feedback is given by connecting a resistance Rf between
the output and the inverting input terminals.
• Negative feed back means the returning signal has a phase that
opposes the input signal.
• The feed back, in this case, is voltage shunt feed back.
• Let V3 be the source voltage,Vi be the differential input voltage
(voltage at s)and Vo be the output voltage.

7. Derivation:

8. The gain of the amplifier with feedback is A=Vo/Vs
. So,A= -Rf/R
• Thus the closed loop gain of the amplifier depends on the
feedback resistance and resistance in the output.
• The negative sign indicates that the output is in inverted with
respect to the input i.e.,there is phase reversal of 180degree in the
input.
• The output is stable due to negative feedback.

9. Advantages:
• It follows the negative feedback.So the gain factor of these
amplifier is very high.
• The output generated will be out of phase with the applied input
signal.
• The potential values at both the inverting and non-inverting
terminals are maintained at zero.

10. Disadvantages:
• The gain is high but the feedback that is followed must be
maintained to be distortion less.
• The applied input signal should not contain the noise because
small value applied will be multiplied and obtained at the output.

11. THANK YOU