Find the value of input resistance for differential amplifier with one op-amp. If R1 = R2=100Ω and RF = R3 =5kΩ.

(a) RIFx = 110Ω; RIFy = 6.7kΩ

(b) RIFx = 100Ω; RIFy = 5.1kΩ

(c) RIFx = 150Ω; RIFy = 7.2kΩ

(d) RIFx = 190Ω; RIFy = 9.0kΩ

I have been asked this question in an interview for internship.

The above asked question is from Differential Amplifiers with Multiple Op-Amp in division Operational Amplifier Characteristics of Linear Integrated Circuits