Assuming a current mirror is to be biased with Veff =0.4V, how large must the devices be in order to ensure the current mismatch has a standard deviation better than 1%? Assume that AVt0 = 4 mV ⋅ μm and AK' = 0.01 μm.

Question

Assuming a current mirror is to be biased with [latex] \mathrm{V}_{\mathrm{eff}}=0.4 \mathrm{~V}[/latex], how large must the devices be in order to ensure the current mismatch has a standard deviation better than 1%? Assume that [latex] A_{\mathrm{Vt} 0}=4 \mathrm{mV} \cdot \mu \mathrm{m} ext { and } A_{K^′}=0.01 \mu \mathrm{m} ext {. }[/latex].

Accepted Answer

From Fig. 2.26, the 2 μm/0.2 μm device has a standard deviation of 3.2% at [latex] \mathrm{V}_{\mathrm{eff}}=0.4 \mathrm{~V}[/latex]. This will decrease with [latex] \sqrt{\mathrm{WL}}[/latex]. Hence the device must be made [latex] 3.2^2=10.2[/latex] times larger in area. For example, each device could be sized [latex]6.5 \mu \mathrm{m} / 0.65 \mu \mathrm{m} [/latex].

Question 2.4: Assuming a current mirror is to be biased with Veff =0.4V, h......

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