8.75 Figure P8.75 shows a folded-cascode CMOS amplifier utilizing a si

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8.75 Figure P8.75 shows a folded-cascode CMOS amplifier utilizing a simple current source Q2, supplying a current 2I, and a cascaded current-source (Q4, Q5) supplying a current I. Assume, for simplicity, that all transistors have equal parameters, gm and ro. (50pt) (a) Give approximate expressions for all the resistances indicated (b) Find the amplifier output resistance Ro. (5pt) (c) Show that the short-circuit transconductance Gm is approximately equal to gm1. Note that the short-circuit transconductance determined by short-circuiting vo to ground and finding the current that flows through the short circuit, Gmvi (5pt) (d) Find the overall voltage gain vo/vi and evaluate its value for the case gm1 = 2 mA/V and intrinsic gain, A0 = 30.

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8.75 Figure P8.75 shows a folded-cascode CMOS amplifier utilizing a simple current source Q2, supplying a current 2I, and a cascaded current-source (Q4, Q5) supplying a current I. Assume, for simplicity, that all transistors have equal parameters, gm and ro. (50pt) (a) Give approximate expressions for all the resistances indicated (b) Find the amplifier output resistance Ro. (5pt) (c) Show that the short-circuit transconductance Gm is approximately equal to gm1. Note that the short-circuit transconductance determined by short-circuiting vo to ground and finding the current that flows through the short circuit, Gmvi (5pt) (d) Find the overall voltage gain vo/vi and evaluate its value for the case gm1 = 2 mA/V and intrinsic gain, A0 = 30.

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Figure P7.33 shows a discrete-circuit amplifier. The input signal vsig is coupled to the gate through a very large capacitor (shown as infinite). The transistor source is connected to ground at signal frequencies via a very large capacitor (shown as infinite). The output voltage signal that develops at the drain is coupled to a load resistance via a very large capacitor (shown as infinite). All capacitors behave as short circuits for signals and as open circuits for dc. (a) If the transistor has Vt = 1 V, and kn = 4 mA/V2 , verify that the bias circuit establishes VGS = 1.5 V, ID = 0.5 mA, and VD = +7.0 V. That is, assume these values, and verify that they are consistent with the values of the circuit components and the device parameters. (b) Find gm and ro if VA = 100 V. (c) Draw a complete small-signal equivalent circuit for the amplifier, assuming all capacitors behave as short circuits at signal frequencies. (d) Find Rin, vgs/vsig, vo/vgs, and vo/vsig.

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