What is an operational amplifier?

"Op Amp" is an abbreviation for operational amplifier. Ideally, this is a differential amplifier with the following characteristics:

• Gain: infinite
• Input impedance: infinite
• Output impedance: 0
• Delay from input to output: 0

By negative feedback^Note application, it can be used as an amplifier and for various types of analog signal processing (addition, subtraction, differentiation, integration, etc.).

[Operational amplifier description]
Represented as a triangle, comprises a total of 5 pins, as follows: + input (V_N: non-inverting input => This means that the polarities of the applied input signal and the signal obtained as the output are identical), - input (V_I: inverting input: This means that the polarities of the applied input signal and the signal obtained as the output are exactly the opposite (-180°)), output (V_O), and power supplies (V⁺, V^-).



The most common usage example is that of an amplification circuit, as follows.



In this example, the input signal is amplified by (1 + R₂/R₁) times.
If R₁ = 1 kΩ and R₂ = 10 kΩ, the amplifier will have a gain of x11.
Therefore, the gain can be freely set simply by changing the resistance value. In the above circuit, the signal is being input via the + pin, so the input and output are in-phase (non-inverting amplifier); however, if the signal is input on the R₁ side, the output is inverted (inverting amplifier).

Note Negative feedback means the output signal is fed back to the - input via a resistor, capacitor, diode, or transistor connected between the output and - input.