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MELZG 632 Assignment 1

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MELZG 632: Analog IC Design
Assignment 1
Submission Date: 18th August 2019
Note: Until and otherwise stated use the device data given in table at the end of this
document and assume 𝑽𝑫𝑫 = πŸ‘ 𝑽 where necessary.
1. Sketch 𝐼𝑋 and transconductance of the transistor as a function of 𝑉𝑋 for each circuit
given as 𝑉𝑋 varies from 0 to 𝑉𝐷𝐷 .
2. Sketch π‘‰π‘œπ‘’π‘‘ as a function of 𝑉𝑖𝑛 for the circuit given as 𝑉𝑖𝑛 varies from 0 to 𝑉𝐷𝐷 .
3. Sketch 𝑉𝑋 and 𝐼𝑋 as a function of time for the circuit given. The initial voltage of 𝐢1
is equal to 3 V.
4. The transit frequency, 𝑓𝑇 , of a MOSFET is defined as the frequency at which the
small-signal current gain of the device drops to unity while the source and drain
terminals are held at ac ground. Prove that
𝑓𝑇 =
π‘”π‘š
2πœ‹(𝐢𝐺𝐷 + 𝐢𝐺𝑆 )
Note that 𝑓𝑇 does not include the effect of S/D junction capacitance.
5. Explain why the structures cannot operate as current sources even if they are in
saturation.
6. An NMOS device is operating in the subthreshold region has a ΞΆ of 1.5. What
variation in 𝐢𝐺𝑆 results in a ten-fold change in 𝐼𝐷 ? If 𝐼𝐷 = 10 µ 𝐴, what is π‘”π‘š ?
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