Sheet 1 of 2

Common-Emitter/Source Circuits Common-emitter BJT circuit The figure below shows the simplied ‘Pi’ model of a common-emitter BJT.

Vout

Vin = Vbe

E

B C

Rbe

Rce

Β.ib -gm.Vbe

ib

Vbe

b

e

c

Vin Vout

Zin

Zout

RL

RL

(mS) ctanceTranscondu Kelvin in eTemperatur T

1.6022x10 charge Electron q

1.3807x10 constant Boltzmans k whereq

k.T V; VI whereR

19-

123-T

T

CQIN

==

==

===== −

gm

C

JKgmgmβ

ge(V)EarlyVolta V WhereIV rceR ACQ

AOUT ===

T

A

CQ

A

T

CQ

be

be

IN

OUTV V

V IV.

VI

rce. V

rce.V.

VV

A ==−=−

== gmgm

ββ - i.i-

II A

b

b

IN

OUTi ===

Sheet 2 of 2

Common-Source MOS FET Circuit

RL

gate

source

drain

Vout

Vin

Vin

g

gmVin

s

d

rds

RL

Io

Vout

Voltage Gain Av

( )

Rr

.Rrgm- A //RrgmV- V

VV A

Lds

LdsLdsINO

IN

OV

⎟⎟⎠

⎞⎜⎜⎝

⎛+

==

=

Input Resistance RIN = ∞ Output Resistance

LdsO

OOUT //Rr

IV R ==

Current Gain Ai Ai = ∞