Characteristics of Ideal Operational Amplifiers:
- Open loop Voltage Gain A0 is infinity.
- Infinity input resistance Ri so that almost any signal source can
drive it and there is no loading of the preceding stage.
- Zero output resistance R0 so that the output can drive an infinite
the number of other devices.
- Perfect Balance, i.e. the differential voltage in inverting and
non-inverting terminals are zero.
- Zero output voltage when the input is zero.
- Infinity bandwidth so that any frequency signal from 0 to ∞ Hz can
be amplified without attenuation.
- Infinity common-mode rejection ratio so that the output common-mode
noise voltage is zero.
- Infinity slew rate so that output voltage changes occur
simultaneously with input voltage changes.
- Zero drift of characteristics with temperature.
Characteristic of Practical Op-amp
- The open loop voltage gain A0 is maximum and finite, a typical value
for the practical op-amp is considered to be 200,000.
- The input impedance Zi is maximum and is finite i.e. in the order
of 100k or more.
- The output impedance Z0 is minimum, not zero, in the order of 100 or
- The CMRR is maximum and finite.
- Bandwidth is maximum and finite i.e. it can amplify dc to 1 MHz
- A slight drift of characteristics due to the change in temperature
, not null.
- Two terminal may be virtually ground, not Vd = 0 exactly, for all
- Maximum slow-rate and has the finite value.
- The output is negligible due to dc-bias when the input is zero.