The input impedance of an ideal Op-amp is ______.

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RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)
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  1. 100 Ω 
  2. Infinite
  3. Unity
  4. Zero

Answer (Detailed Solution Below)

Option 2 : Infinite
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The correct answer is option 2.

Operational Amplifier

F1 Engineering Savita 5-4-23 D11

An Operational Amplifier is basically a three-terminal device that consists of two high-impedance inputs.

One of the inputs is called the Inverting Input, marked with a negative or “minus” sign, ( – ). The other input is called the Non-inverting Input, marked with a positive or “plus” sign ( + ).

The output of the OP-AMP is given by:

\(V_o=A_{OL}({V_+-V_-)}\)

where, AOL = Gain of OP-AMP

V+ = Input at the non-inverting terminal

V- = Input at the inverting terminal

Characteristics of ideal OP-AMP

  • Infinite input impedance
  • Zero output impedance
  • Infinite voltage gain
  • Infinite CMRR
  • Infinite slew rate
  • Zero offset voltage
  • Zero input bias current
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