Amplifier Circuit Diagrams


High Common Mode Response Rate Instrumentation Amplifier

A High Common Mode Response Rate Instrumentation Amplifier (IC) is a specialized electronic amplifier designed to accurately amplify the difference in voltage between two input signals while rejecting common-mode signals. The common-mode signal refers to any voltage that appears simultaneously on both input terminals of the amplifier. High Common Mode Response Rate refers to the amplifier’s ability to handle a wide range of common-mode voltages without distorting the desired differential signal.


Here’s a breakdown of the key components of this definition:

Instrumentation Amplifier:

  • An instrumentation amplifier is a type of operational amplifier (op-amp) configuration that is optimized for applications where precise amplification of small differential signals is required. It typically consists of multiple op-amps and provides high input impedance, high common-mode rejection, and adjustable gain.

High Common Mode Response Rate:

  • This phrase emphasizes the amplifier’s capability to maintain accurate operation even when exposed to large common-mode voltages. In practical applications, common-mode voltages can often be present due to noise or interference, and a high common-mode response rate ensures that the amplifier effectively rejects these unwanted signals.

In the context of instrumentation amplifiers, having a high common-mode rejection ratio (CMRR) is a valuable characteristic because it enables precise amplification of differential signals while effectively suppressing common-mode noise. In this post, we will explore a schematic circuit diagram designed for an instrumentation amplifier with excellent CMRR.

The circuit for the instrumentation amplifier is constructed using three operational amplifiers (op-amps) and a set of precision resistors. The fundamental design of the circuit includes two input terminals: one for the non-inverting signal (V1) and the other for the inverting signal (V2). The output of the third op-amp is connected to the junction point of two resistors, which is where the final output signal is derived. Now, let’s delve into a more detailed examination of this circuit.


  1. A differential amplifier is connected to the first operational amplifier, where the non-inverting input (V1) is linked to the inverting terminal via a resistor (R1), and the inverting terminal (V2) is directly connected to the inverting input (V2). This configuration rejects common-mode voltage while amplifying the differential voltage (V1 – V2).
  2. A unity-gain buffer is connected to the second operational amplifier, with its non-inverting input linked to the output of the first op-amp. This buffer offers high input impedance and low output impedance, isolating the initial stage from the subsequent stages.
  3. Similar to the first stage, the third operational amplifier is configured as a differential amplifier. Its inverting input is directly connected to the inverting terminal, and its non-inverting input is connected to the inverting terminal through a resistor (R3). This stage rejects common-mode voltage while further amplifying the differential voltage.
  4. The output is generated at the junction of two resistors (R2 and R4) connected to the output of the third operational amplifier. The gain of the instrumentation amplifier is determined by these resistors.

Cascading the two differential amplifier stages greatly enhances the Common-Mode Rejection Ratio (CMRR) of the instrumentation amplifier. Additionally, the use of high-quality operational amplifiers and precision resistors helps maintain accuracy and stability.

It’s important to note that the specific values of components and the choice of operational amplifiers may vary depending on the requirements of the individual application and desired performance standards.


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