Write a note on closed loop gain of an Op-Amp.

Closed-Loop Gain of an Op-Amp:

The closed-loop gain of an operational amplifier (Op-Amp) refers to the ratio of the output voltage to the input voltage when the Op-Amp is configured in a negative feedback loop. It is an essential parameter that determines the overall amplification and response of the Op-Amp circuit.

Gain Equation:

In a closed-loop Op-Amp circuit, the closed-loop gain ($A_{CL}$) is determined by the feedback network components. For an inverting amplifier configuration, the closed-loop gain is given by:

$$A_{CL} = -\frac{R_f}{R_i}$$

where:

• $R_f$ is the feedback resistor
• $R_i$ is the input resistor

For a non-inverting amplifier configuration, the closed-loop gain is given by:

$$A_{CL} = 1 + \frac{R_f}{R_i}$$

Key Points:

• The closed-loop gain of an Op-Amp is determined by the feedback network components and is independent of the Op-Amp's open-loop gain.
• The negative sign in the inverting amplifier configuration indicates a phase inversion between the input and output signals.
• The non-inverting amplifier configuration provides a positive gain without phase inversion.
• The closed-loop gain can be adjusted by changing the values of $R_f$ and $R_i$.

Applications:

• Closed-loop Op-Amp circuits are widely used in various applications, including:
  • Signal amplification
  • Voltage buffering
  • Summing and differencing amplifiers
  • Active filters
  • Oscillators
  • Comparators

Advantages:

• The closed-loop configuration provides high stability and accuracy in the Op-Amp's operation.
• The closed-loop gain is independent of the Op-Amp's open-loop gain variations, making the circuit more predictable and reliable.
• Negative feedback reduces the non-linearity and distortion introduced by the Op-Amp.

Conclusion:

The closed-loop gain of an Op-Amp is a crucial parameter that determines the overall performance of the circuit. By carefully selecting the feedback network components, designers can achieve precise and stable amplification, filtering, and other desired operations.