Question

Which of the following electric characteristics is not exhibited by an ideal op-amp?
A) Infinite voltage gain
B) Infinite bandwidth
C) Infinite output resistance
D) Infinite slew rate

Answer 1

Operational amplifier is an integrated circuit that is used to amplify weak electric signals. An ideal operational amplifier is a device which has certain special characteristics. This includes characteristics such as zero offset, zero output resistance and many more. To answer the above question, recall all the characteristics of an ideal operational amplifier.

Complete step by step answer:
In an ideal op-amp any voltage differential on the two input terminals will result in an infinite voltage on the output. In real op-amps, the output voltage is limited by the power supply voltage. Hence statement of option A is true.
Also in an ideal operational amplifier there is an infinite frequency response and it can amplify any frequency signal from DC to the highest AC frequencies so it is therefore assumed to have an infinite bandwidth. Hence option B is also true for an ideal operational amplifier.
For resistance, the output impedance of an ideal operational amplifier is zero. This means that regardless of the amount of current drawn by an external load, the output voltage of an operational amplifier will remain unaffected. That is, no loading occurs. Hence option C is false.
Therefore Option C is the correct answer.
Slew rate is defined as the maximum rate of change of an operational amplifier's output voltage and is given in the units of volts per microsecond. It is measured by applying a large signal step to the input of the op amp, and measuring the rate of change of the output signal's amplitude.

Note: Read the question carefully. The question asks for an incorrect statement. It must be noted that ideal operational amplifiers are not practical as in real life there are certain limitations. Moreover it is not possible to obtain infinite resistance and infinite bandwidth in practical situations.