2.15 Consider the difference-amplifier circuit of Fig. 2.16 for the case R1 = R3 = 2 kΩ and R2 = R4 = 200 kΩ. (a) Find the value of the differential gain Ad. (b) Find the value of the differential input resistance Rid and the output resistance Ro. (c) If the resistors have 1% tolerance (i.e., each can be within ±1% of its nominal value), use Eq. (2.19) to find the worst-case common-mode gain Acm and hence the corresponding value of CMRR. (a) 100 V/V (40 dB); (b) 4 kΩ, 0 Ω; (c) 0.04 V/V, 68 dB