OpAmp Gain Calculator
Use Omni's opamp gain calculator to determine the voltage gain of an operational amplifier. You can use this opamp calculator to find out the voltage gain of an inverting opamp as well as a noninverting opamp. If you want to know what an opamp is or how to calculate the gain of an opamp, read on. You will also find out more about what opamps are used for and the characteristic of an ideal opamp.
What is an opamp (operational amplifier)?
Opamps or operational amplifiers are electronic devices that amplify an electric signal. They are the basic building blocks of every analog electronic circuit. Opamps perform a range of mathematical operations in analog circuits, for example, addition, integration, differentiation, comparison, etc. In addition, we also use them extensively in signal filtering and conditioning.
Gain of an opamp
A typical opamp (see figure 1) is basically a device with two input terminals and one output terminal. The input terminal with a negative (
) sign is called the inverting terminal. The input terminal with a positive (+
) sign is called a noninverting terminal. Both input terminals have very high electrical impedance. The third terminal is the output terminal from which we receive the output voltage or current signal. The impedance of the output terminal is almost zero.
An opamp basically amplifies the difference between the two input signals, V_{inv}
and V_{noninv}
. The gain A
of a linear operational amplifier is the ratio of the output voltage to the input voltage:
A = V_{out} / V_{in}
where:
V_{in} = V_{inv}  V_{noninv}
Types of opamp configuration
In opamp circuits, we usually implement a feedback mechanism by using some external components like resistors or capacitors. Thus, the operation of an opamp depends on the type of feedback mechanism (whether positive or negative) and the feedback component employed.
To implement negative feedback, we take a portion of the output signal and feed it back to the inverting input terminal through an external feedback resistor. This feedback connection forces the differential input voltage of the opamp to become zero, i.e., V_{inv} = V_{noninv}
.
Two basic operational amplifier circuit configuration are:

Inverting opamp: Figure 2 shows a circuit diagram of an inverting operational amplifier. In inverting configuration, we connect the input signal to the inverting terminal through resistance
R_{in}
and ground the noninverting terminal. The feedback resistanceR_{f}
feeds part of the amplified output signal back to the input. The voltage gain of an inverting opamp is:A_{inv} = V_{out} / V_{in} =  R_{f} / R_{in}
The negative sign means that the output is 180° out of phase with the input.

Noninverting opamp: Figure 3 shows a circuit diagram for a noninverting operational amplifier. Here, we apply the input signal directly to the noninverting terminal. To apply negative feedback, we connect the resistances
R_{2}
andR_{1}
to the inverting terminal. The voltage gain of a noninverting opamp is:A_{noninv} = V_{out} / V_{in} = 1 + R_{2} / R_{1}
In noninverting opamps, the input and output are in the same phase.
How to find the gain of an opamp?
Let us see an example of how to calculate the voltage gain using the opamp gain calculator. We will consider an inverting opamp with input resistance 1 kΩ and feedback resistance of 10 kΩ.
 Choose the type of opamp, e.g., inverting, from the dropdown menu.
 Enter the values of input resistance (1 kΩ) and feedback resistance (10 kΩ).
 The opamp calculator will display the voltage gain of the opamp, e.g., 10.
 If you select noninverting opamp, the calculator will show 11.
FAQ
What are the characteristics of an ideal opamp?
The characteristic of an ideal opamp are:
 Infinite input impedance;
 Zero output impedance;
 Infinite voltage gain; and
 Infinite bandwidth.
What are opamps used for?
Opamps are mostly used as signal amplifiers in electronic circuits. Some common applications/use of opamps are:
 To perform mathematical operations like addition, integration, differentiation, etc.
 In signal conditioning, for example, as a filter, rectifier, etc.
 As a current to voltage (or voltage to current) converter.
What is thermal drift in opamp?
Thermal drift is the change in the normal operation of an opamp due to a change in the external temperature. The gain, impedances (input and output), frequency response, and voltages of the opamp change with temperature.
Operational amplifiers are electronic devices made using semiconductor components (e.g., transistors). As the properties of semiconductors strongly depend on temperature, any change in the external ambient temperature also influences the operational behavior of devices manufactured using them.
Why is an opamp is called a differential amplifier?
An opamp amplifies the difference of the two input voltage signals, hence the name differential amplifier.