Basics of Opamp (Operational amplifier)


##What is an Opamp?

Op-amp is a differential amplifier, which amplifies the difference in voltage inputs at the two terminal of the opamp and produces a single-ended output. Op-amp amplifies the difference between the two signal and dimish the common signal. This device is an amplifier intent for use the external feedback elements, where these elements determine the resultant operation. This gives the name operational amplifier.

An op-amp comes under the monolithic ICs( integrated circuits) and has advantages like small size, less power consumption, high reliability etc.


An external power supply is needed for the operation of the opamp, represented as positive and negative terminals of the op-amp.

##Internal diagram of Op-amp:

##Characteristics of Op amp:

  • Infinte input impedence - No current into inputs

  • Low output impedence

  • Large voltage gain at low frequency - Voltage difference between two terminals are magnified to a very large extent)

  • Infinite bandwidth ( almost all frequency can be amplified by same factor) - bandwidth limited to a few MHz

  • No slew rate no delay between change in input and change in output. The rate of change of the output of an opamp is limited.

##Block diagram of Op-amp:

Input side: Provide most of the voltage gain of Op-amp and decides input resistance.

Intermediate stage: is another differential amplifier which is driven by output of the input stage.

Level shifting stage: Due to the direct coupling of first two stages, the input of level shifting is an amplified signal with some non zero dc signal. Level shifting is used to bring this dc level to zero volts with respect to ground.

Instrumentation amplifier and it's applications