## Description

1

Ve311 Homework #3

Note:

(1) Please use A4 size papers.

(2) Please use the SPICE model below for simulation.

.model Qbreakn NPN IS=4e-16 BF=100 VAF=50

1. [BJT Forward-Active I-V Characteristics] For a npn BJT circuit as below:

(a) [20%] When VBE = 0.7 V and VCE = 2 V , use proper equations

provided in the course slides and the spice model above to calculate

the gm and ro.

(b) [10%] In Pspice, when VCE = 2 V, plot IC versus VBE (increasing

from 0 to 1 V). Find out the slope at VBE = 0.7 V and compare it with

the gm value calculated in (a).

(c) [10%] In Pspice, when VBE = 0.7 V, plot IC versus VCE (increasing

from 1 to 3 V). Find out the inverse of the slope at VCE = 2 V and

compare it with the ro value calculated in (a).

2

2. [BJT Common-Emitter Amplifier] For a npn BJT circuit as below:

(a) [30%] When VIN = 0.7 V , use proper equations provided in the

course slides and the spice model above to calculate the small-signal

voltage gain (Aυ =

υout

υin

). Hint: take Early Effect into consideration.

(b) [15%, DC Sweep] In Pspice, plot VOUT versus VIN (increasing from 0

to 1 V). Find out the slope at VIN = 0.7 V and compare it with the

voltage gain calculated in (a).

(c) [15%, Transient Analysis] In Pspice, when Vin = 0.7 + 0.001 ∙

sin(2π100 ∙ time) V, plot Vout and Vin versus time (from 0 to 0.1

second). Find out |Aυ

| = |

υout

υin

| and compare it with the voltage gain

calculated in (a).