Home / How to Guide / Whats an operational amplifier and how does it work ?

Whats an operational amplifier and how does it work ?

An operational amplifier (op-amp) is a versatile and widely used electronic component that plays a crucial role in analog signal processing and amplification circuits. It is a high-gain voltage amplifier with differential inputs and a single output. Op-amps are characterized by their ability to amplify the voltage difference between the two input terminals.

Key Characteristics of an Operational Amplifier:

  1. Differential Inputs:
    • Op-amps have two input terminals, commonly labeled as the inverting (-) and non-inverting (+) inputs. The voltage difference between these inputs determines the amplifier’s output.
  2. High Input Impedance:
    • Op-amps typically have a very high input impedance, meaning they draw minimal current from the input signal source.
  3. Low Output Impedance:
    • Op-amps have a low output impedance, allowing them to deliver a relatively high current to the connected load.
  4. High Open-Loop Gain:
    • The open-loop gain of an op-amp is extremely high, often exceeding 100,000. This means even small voltage differences at the inputs can lead to large output voltages.
  5. Differential and Common-Mode Signals:
    • Op-amps amplify the difference between the inverting and non-inverting inputs (differential mode) while rejecting the common-mode signals (signals present at both inputs with the same voltage).
  6. Negative Feedback:
    • Negative feedback is a common feature in op-amp circuits. It involves feeding a portion of the output signal back to the inverting input. Negative feedback stabilizes the amplifier’s performance, reduces distortion, and improves linearity.

Internal Circuitry:

The internal circuitry of an op-amp may include the following components:

  1. Differential Amplifier:
    • The core of an op-amp is a differential amplifier, which amplifies the voltage difference between the inverting and non-inverting inputs.
  2. High-Gain Stage:
    • A high-gain stage further amplifies the differential voltage. This stage contributes to the op-amp’s overall high open-loop gain.
  3. Output Stage:
    • The output stage is responsible for delivering the amplified signal to the external circuit. It often includes a push-pull configuration for efficient current delivery.
  4. Compensation Network:
    • Internal compensation networks are used to stabilize the op-amp and prevent high-frequency oscillations.

Operational Amplifier Modes:

  1. Inverting Amplifier:
    • In this configuration, the output is inverted concerning the input signal. It is achieved by connecting the input signal to the inverting (-) input and providing feedback from the output to the inverting input.
  2. Non-Inverting Amplifier:
    • The output signal is in-phase with the input signal in this configuration. The input is connected to the non-inverting (+) input, and feedback is applied from the output to the inverting input.
  3. Comparator:
    • In comparator mode, the op-amp is used to compare two input voltages. The output switches between high and low states based on the relative magnitudes of the inputs.
  4. Integrator and Differentiator:
    • By using additional components, op-amps can be configured as integrators or differentiators to perform mathematical operations on the input signals.


  1. Input Difference:
    • The op-amp amplifies the voltage difference between its inverting and non-inverting inputs.
  2. Output Voltage:
    • The output voltage (�outVout​) is proportional to the input voltage difference (�in, diffVin, diff​) multiplied by the open-loop gain (�OLAOL​).

    �out=�OL⋅�in, diffVout​=AOL​⋅Vin, diff​

  3. Negative Feedback:
    • In circuits with negative feedback, part of the output voltage is fed back to the inverting input. This feedback, when properly designed, stabilizes the circuit, sets the closed-loop gain, and ensures linear operation.


Operational amplifiers find applications in various electronic circuits, including:

  • Amplifiers: Used for signal amplification.
  • Filters: Employed in active filter circuits.
  • Comparators: Used for signal comparison.
  • Oscillators: Employed in oscillators for signal generation.
  • Mathematical Operations: Configured as integrators and differentiators for mathematical operations.


Operational amplifiers are fundamental building blocks in analog electronics, offering high gain, versatile functionality, and compatibility with negative feedback for stable operation. Their widespread use in diverse applications makes them a cornerstone of electronic circuit design. Understanding the principles of op-amp operation is crucial for designing and analyzing analog circuits.

Recent Updates