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Instrumentation Amplifier

Calculate the output voltage of a three op-amp instrumentation amplifier.

A instrumentation amplifier is a precision amplifier circuit intended to reject common-mode noise and precisely amplify small differential signals. It typically features a differential amplifier design with three operational amplifiers and precision resistors arranged to provide:

High input impedance
Low output impedance
High Common-Mode Rejection Ratio (CMRR)

An instrumentation amplifier's main function is to attenuate noise and common-mode signals while amplifying weak differential signals from sensors, transducers, or other sources. It offers accurate signal conditioning and amplification for measuring and processing small electrical signals in a variety of instrumentation and measurement systems.

Understanding Instrumentation Amplifiers

Key Characteristics

Characteristic	Description
High Input Impedance	Enables amplification of weak signals without imposing a load on the source
Low Output Impedance	Well-suited for driving a diverse array of loads
High CMRR	Effectively rejects signals common to both inputs, such as noise and interference
Low Self-Generated Noise	Suitable for applications where noise is a critical concern
Low Offset Drift	Output voltage remains stable despite variations in time and temperature
Gain Adjustment	Gain can be adjusted by varying a single resistor, simplifying customization for specific applications

Types of Instrumentation Amplifiers

Type	Description
Three-Op-Amp	The most prevalent type — employs three operational amplifiers to amplify the difference between two input signals
Two-Op-Amp	Utilizes two operational amplifiers; requires higher gain to attain equivalent amplification compared to a three-op-amp design
Chopper-Stabilized	Employs a switching-input frontend to eliminate DC offset errors and drift
Feedback-Free	Utilizes a high-input-impedance differential amplifier without an external feedback network, enabling reduced noise and enhanced bandwidth

Applications

Sensor Signal Conditioning
Data Acquisition Systems
Medical Instruments
Bridge Circuits
Signal Processing and Control

About This Calculator

This online electrical calculator helps determine the output voltage of an instrumentation amplifier using the supplied voltages and variable resistors. Simply enter the necessary values to compute the desired output voltage — useful for both analysis and design of instrumentation amplifier circuits.

Formula

$V_o = (V_2 - V_1) \times \left(1 + \frac{2 \times R_1}{R_g}\right) \times \frac{R_3}{R_2}$

where:

$V_o$ = Output Voltage (V)
$V_1$ = Input Voltage 1 (V)
$V_2$ = Input Voltage 2 (V)
$R_g$ = Resistor Gain (Ω)
$R_1$ = Resistor 1 (Ω)
$R_2$ = Resistor 2 (Ω)
$R_3$ = Resistor 3 (Ω)

Inputs

Voltage V1(V)

Input voltage V1 in volts

Voltage V2(V)

Input voltage V2 in volts

Resistor R1(Ω)

R1 resistor value in ohms — paired with Rg to set gain

Resistor R2(Ω)

R2 resistor value in ohms — output stage resistor

Resistor R3(Ω)

R3 resistor value in ohms — output stage resistor

Resistor Gain Rg(Ω)

Gain resistor Rg in ohms — controls overall amplifier gain

Results

⚠R2 must be greater than zero

Output Voltage—VInstrumentation amplifier output voltage in volts