# BiCMOS Diff-Amp

The BiCMOS circuit in Figure P11.57 is equivalent to a pnp bipolar transistor with an infinite input impedance. The bias current is Iq=900uA. The transistor parameters are :Kp=1ma/V^2, Vtp=-1V, and lambda=0 for M1; and Beta=100, Vbe(on)=.7, and Va=infinity for Q2. [a] Sketch the small-signal equivalent circuit (mine didn't work out, two dependant currents pointed to each other..), [b] Determine the small-signal parameters for each transistor, and [c] Determine the small-signal voltage gain AV=Vo/Vi.

My currents don't work out, so my ss values are too suspect. Please work this out and tell me how you did it.

Thank you.

The practice problem didn't specify which small signal values. However, The values I got from working another bcmos problem were Gm,Vpi,ro,Rpi, gcm, and composite transcondutance.

I guess I'm looking for the small signal voltage gain and the small signal equivalent circuit. The book is obscure.

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#### Solution Summary

The BiCMOS circuit in Figure P11.57 is equivalent to a pnp bipolar transistor with an infinite input impedance. The bias current is Iq=900uA.