An ideal op-amp would exhibit the following characteristics

1. Infinite Voltage gain,A
2. Infinite input resistance,Ri so that almost any signal source can drive it and there is no loading of the preceding stage
3. Zero output resistance,Ro so that output can drive infinite number of other devices
4. Zero output voltage when input voltage is zero
5. Infinite bandwidth so that any frequency signal from zero to infinite Hertz can be amplified without attenuation
6. Infinite common mode rejection ratio(CMRR)so that the output common mode noise voltage is zero
7. Infinite slew rate so that the output voltage changes occur simultaneously with input voltage changes

Equivalent Circuit of an Op-Amp

Output volatge,Vo=AVid=A(V1-V2)

Vid=difference input voltage

V1= Voltage at the non-inverting input terminal with respect to ground

V2= voltage at the inverting terminal with respect to ground

Polarity of the output voltage depends on the polarity of the difference voltage.

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