This post answers the question :”What is an operational amplifier?”. In digital electronics, operational amplifiers are used in a broad range of applications. 

The ideal op amplifier is a differential amplifier with infinite open- loop gain, infinite input impedance, zero output impedance, infinite bandwidth and zero noise.

It has two terminals and one is a negatively marked terminal and it’s called an inverting terminal (V1). And the other is a positively marked terminal called as non inverting terminal (V2) and there is one output there (V0). 

So above we discussed what is an ideal operational amplifier. Here below we will cover characteristics of op amplifier. Ideal operational amplifier has the following characteristics:

Infinite Open Loop Gain

  • It is gained without feedback
  •  AV=V0Vd
  • It should be infinite to get maximum voltage of +Vcc or Vcc
  • Gain is high because it’s designed to have high gain using multistage differential amplifiers

Infinite Input Impedance

  • Due to infinite input impedance 
  • No current flows in the input terminals
  • The operational amplifier can be driven by almost any source
  • There is no loading of source

Zero Output Impedance

  • Due to zero output impedance there will not any change in output voltage due to change in load current
  • That means it can drive any number of loads or devices ideally

Infinite Bandwidth

  • Bandwidth is infinite means it can amplify all frequency signals from zero to infinite
  • So the gain of amplifier remains constant from zero to infinite
  • Therefore operational amplifier can amplify dc as well as ac signals

Zero Offset Voltage

  • Presence of small output voltage through input voltage is zero is called as offset voltage
  • Ideally offset voltage is zero means zero output voltage for zero input voltage i.e equation_4.pdf= equation_5.pdf= 0

Infinite Common Mode Rejection Ratio (CMRR)

  • The ratio of differential gain to common mode gain as defined as Common Mode Rejection Ratio (CMRR)
  • Infinite CMRR ensures zero common mode gain
  • So the common mode noise output is zero for ideal operational amplifier
  • CMRR=AdAc

 Infinite Slew Rate

  • Infinite slew rate ensures that the changes in output voltage occur simultaneously with the changes in the output voltage.

Zero Power Supply Rejection Ratio

  • Power supply rejection ratio is the degree of dependence of output voltage on changes in power supply.
  • PSRR = 0 means the output voltage does not change with fluctuations in supply voltage.