Homework #9

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1. Derive the equation for Rx. Include ro.

(a)

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(b)

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2. Derive the equation for Rx. Include ro.

(a)

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(b)

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3. Derive equations for the output resistance

(seen at the drain of Q2) which

includes ro, and overall gain of the

MOS cascade amplifier below

(Vout at the drain of Q2/Vin

at gate of Q1).

Fall 2010

4. Design the cascade amplifier shown

gm1=1mA/V and Ro=400kΩ. Use a 0.18

Vtn=0.5 V, VA’=5V/µm and k’n=400µ

and I. Use identical transistors operated at Vov=0.2V, and design

for the maximum possible negative signal swing at the

output(when VDS=Vov). What is the value of the minimum

permitted output voltage?

Homework #9

he cascade amplifier shown at the right to obtain

Use a 0.18µm technology for which

µA/V2. Determine L, W/L, VG2,

. Use identical transistors operated at Vov=0.2V, and design

for the maximum possible negative signal swing at the

t is the value of the minimum

8

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5. For the four possible realizations of the folded cascade amplifier shown below, assume that the BJTs

have β=100 and that both the BJTs and the MOSFets have |VA|=5V. Let I=100µA, and assume that the

MOSFets are operating at |VOV|=0.2V. Assume ideal current sources. For each circuit determine Rin,

Rout, and Avo=vo/vI. Comment on your results.

(a)

(b)

(c)

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(d)

6. The transistors in the circuit below have

(a) Find Rin, Rout, and the overall voltage gain.

(b) What is the effect of increasing the bias currents by a factor of 10 on Rin, the overall gain, and the

power dissipation?

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6. The transistors in the circuit below have β=100 and VA=100V.

Find Rin, Rout, and the overall voltage gain.

(b) What is the effect of increasing the bias currents by a factor of 10 on Rin, the overall gain, and the

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(b) What is the effect of increasing the bias currents by a factor of 10 on Rin, the overall gain, and the

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7. In each of the six circuit below, let

problems)

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7. In each of the six circuit below, let β=100 and neglect ro. Calculate the overall voltage gain. (worth 2

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. Calculate the overall voltage gain. (worth 2

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8. Consider a bipolar cascode amplifier biased at a current of 1mA. The transistors used have β=100,

ro=100kΩ, Cπ=14pF, Cµ=2pF, CCS=0pF. The amplifier is fed with a signal source having Rsig=4kΩ. The

load resistance RL=2.4kΩ. Find the low frequency gain AM, and estimate the value of the 3dB frequency

fH.

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9. A BJT cascade amplifier uses transistors for which β=100, VA=100V, fT=1GHz, and Cµ=0.1pF. It

operates at a bias current of 0.1mA between a source with Rsig=rπ and a load RL=βro. Let CL=CCS=0pF

and find the overall voltage gain at dc, fH and ft.