# hw08 - ECE 3150 Homework 8 1. Due 4/3/2009 in the drop box...

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ECE 3150 Homework 8 Due 4/3/2009 in the drop box 1. (Cascode amplifier derivation) Use Fig. 5.29 for the MOSFET cascode amplifier considering the Early effect but ignore the body effect, (a) Use the small-signal KCL to derive R out = r o2 + A vo2 r o1 and R in2 = 1/g m2 + R L /A vo2 . Confirm this result with the intuitive observation in Fig. 5.29. (4 pts) (b) If Q 1 and Q 2 are identical, derive A v = -A 0 2 R L /(R L + A 0 r o ) with A 0 defined as g m r o . (4 pts) (c) If Q 1 and Q 2 have different W but the same L (still both are in saturation), if we want a larger R out , which transistor should be larger? (4 pts) 2. (Cascode as shielding point of view) Following Question 1, the cascode transistor Q 2 can be thought of as providing a “shield” for the input transistor Q 1 from the voltage variation at the output. For the cascode circuit below, we have grounded the input terminal (i.e., reduce the small-signal input v i to zero). Apply a small change v x to the output node, and denote the voltage change that results at the

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## This note was uploaded on 10/25/2009 for the course ECE 3150 taught by Professor Spencer during the Spring '07 term at Cornell.

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hw08 - ECE 3150 Homework 8 1. Due 4/3/2009 in the drop box...

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