9.93 This problem investigates the effect of transistor mismatches on the input offset voltage of the current-mirror-loaded MOS differential amplifier of Fig. 9.32(a). For this purpose, ground both input terminals and short-circuit the output node to ground. (a) If the amplifying transistors Q1 and Q2 exhibit a W/L mismatch of (W/L)A, find the resulting short-circuit output current and hence show that the corresponding VOS is given by V OS1 = VOV/2(W/L)A (W/L)A where V OV is the overdrive voltage at which Q1 and Q2 are operating. (b) Repeat for a mismatch (W/L)M in the W/L ratios of the mirror transistor Q3 and Q4 to show that the corresponding V OS is given by V OS2 = VOV/2(W/L)M (W/L)M where V OV is the overdrive voltage at which Q1 and Q2 are operating. (c) For a circuit in which all transistors are operated at V OV = 0.2 V and all W/L ratios are accurate to within ±1% of nominal, find the worst-case total offset voltage VOS.

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