Question

The ideal op-amp has the following characteristics:
A. input resistance= infinity; voltage resistance= infinity
B. input resistance= zero; voltage resistance= infinity
C. input resistance= zero; voltage resistance= zero
D. input resistance= infinity; voltage resistance= zero

Answer 1

Operational amplifier, also known as the op-amp in short, is an integrated circuit which can amplify the input voltage. The amplification of the output voltage is nearly times the input voltage. These are often used in the along circuits.

Complete answer:
An op-amp uses differential input to amplify the input voltage. The two terminals of the op-amp are the non-inverting and the inverting terminal. The op-amp generally amplifies the voltage difference of the two terminals. Also, some of the input voltage is given back to the input.An ideal op-amp must have the following characteristics:
a. infinite open-loop gain
b. infinite input impedance
c. no input offset
d. infinite range of output voltage
e. no noise
f. zero output impedance
g. infinite bandwidth.
From b) we can say that an ideal op-amp must have no loading resistance; this can be achieved by high input resistance. This also reduces the current flowing through the op-amp. Thus we can say that the resistance of an ideal op-amp must be infinite. Similarly, from a) we can say that, an op-amp can amplify the voltage in the circuit. Thus it must have high voltage gain. Then, we can say that it will have infinite voltage gain. The ideal op-amp must have infinite input resistance and infinite voltage gain.

Hence the answer is A. input resistance= infinity; voltage resistance= infinity.

Note:
However, no op-amp is ideal. But the op-amps are temperature independent and have high tolerance. It is a type of differential amplifier. It selects the voltage which doesn't overlap through both the input voltages. Hence we can say that the op-amp selectively amplifies the voltage.