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for an ideal opamp input current is zero,so obviously input impedance is infinity
u refer "opamps and linear integrated circuits" by Ramakant A.Gayakward for basics
for an ideal opamp input current is zero,so obviously input impedance is infinity
u refer "opamps and linear integrated circuits" by Ramakant A.Gayakward for basics
Infinite input impedance will not load the previous stage. The zero output impedance is there for the same reason. Infinite impedance means no current, which means no capacitor charging, thus no slew-rate, higher gains, gfreater accuracy etc.
The same can be said for the zero output impedance, you can't load 0Ohms! 0//anything = 0, thus gain not affected in the sameway x//infinity = x - no loading!!
Any of amplifiers, not only opamp, is expected to be ideal, means that it has infinte input impedance, and zero output impedance.
Infinite input impedance means that the amplifier does not draw current (load) the previous stage. All the previous stage output voltage apply to the amplifier input without current, so the previous stage does not consume additional power from power supply (higher efficiency), and the amplifier does not make input signal distorted.
In the same way, the amplifier with zero output impedance will load all output voltage to the next stage and the output signal will not be distorted.
Dear SWINI,
∞ i/p impedance means it wont load its previous stage........if the input impedance is low or zero, it will cause to draw more current from the previous stage/connected i/p source........so its quite imp to hv very high i/p impedance for any circuit/instrument.
the main reason is internally differential amplifier is input block inside a opamp...it is a well known fact that diifferential amplifier has high input impedance hence the effect....
i think designers want a circuit which should hold high gain high input impedance and so many desirable qualities..so to realise their dreams ,they filled internal circuit with such propery posessing blocks...
hope u understand....
if not reply me
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