Ve311 Homework #8

Note:

(1) Please use A4 size papers.

(2) Please use the SPICE model on page 2 for simulation and calculation.

1. [Current Source and Cascode Current Source]

(a) [20%] (λ ≠ 0 and γ = 0) Derive analytical expressions for the output

impedance of current source (i) and (ii) below.

(b) [40%] (λ ≠ 0 and γ = 0) For VX = 2 V, Va = 1.2 V, Vb = 2.2 V,

(W/L)1 = 20 µm / 2 µm, (W/L)2 = 100 µm / 2 µm, what are the output

impedance values of current source (i) and (ii) below? Does the cascode

structure significantly increase the output impedance?

(c) [10%] What are the minimum values of VX for M1 of circuit (i) and

M2 of circuit (ii) to stay in the saturation region?

(d) [30%] For circuit (i) and (ii) below, plot the IX as a function of VX

(from 0 V to 5 V) using Pspice in DC sweep mode. Confirm whether the

hand-calculation results in (b) and (c) are consistent with the simulation

results here.

2

Vacuum permittivity (𝛜𝐨) = 𝟖. 𝟖𝟓 × 𝟏𝟎−𝟏𝟐 (F / m)

Silicon oxide dielectric constant (𝛜𝐫

) = 𝟑. 𝟗