*2.67 For the difference amplifier of Fig. 2.16, show that if each resistor has a tolerance of ±100% (i.e., for, say, a 5% resistor, = 0.05) then the worst-case CMRR is given approximately by
where K is the nominal (ideal) value of the ratios (R2/R1) and (R4/R3). Calculate the value of worst-case CMRR for an amplifier designed to have a differential gain of ideally 100 V/V, assuming that the op amp is ideal and that 1% resistors are used. What resistor tolerance is needed if a CMRR of 80 dB is required?