1

Lecture 7: Models for Integrated Active Devices

• Notes from – P. Allen, Analog Integrated

Circuits and Systems

• Review of MOS, BJT and Single Transistor Amplifiers

How does the BJT work?

• The BJT base emitter junction is forward biased• A small percentage of electrons crossing the base combine with holes• Electrons that reach the collector depletion region are swept and form the collector current

2

3

Large Signal Model for the BJT (forward Active)

Small Signal BJT

4

MOS Structure

5

Simple Large Signal MOSFET Model

Bulk Effect

6

MOSFET Small-Signal Model

7

8

9

Small-Signal Frequency Dependent Model

10

11

12

13

14

15

16