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# h4 - Homework 4 ECE 403 NCSU Prof Bilbro due before lecture...

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Homework 4, ECE 403, NCSU, Prof. Bilbro due before lecture on Friday, 2/13/09 1) Draw a pmos current mirror with two matched p-channel FETs that is biased with ideal current source I bias , and that is connected to some arbitrary circuit represented only by I out and V out (i.e. you can’t assume anything about the relation between I out and V out .) For concreteness, let’s label the transistors like the current mirror in J&M’s figure 3.4, so that the bias pmos is M3 and the load pmos M2. Show that the low-frequency small-signal model of your current mirror is a simple passive resistor connecting v out to (small-signal) ground with r ds2 = 1 / ( λ pmos I bias ) . 2) Consider the C-S amp from J&M Figure 3.4 and assume that M3 and M2 are matched (i.e. that both of these pmosfets have the same W and L as well as the same current model) . a) Show that the small signal low-frequency gain of this amp is ( 29 1 1 1 0 1 2 2 2 bias bias m V ds ds pmos nmos pmos nmos bias k k I I g A g g I l l l l = - = - = - + + + if the amp is unloaded (i.e. if it’s not connected to any external load.)
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