-
Small signal: only 10% or less variation in IC
-
For the forward active region with fig. 5.13
The simple biasing is not used much in practice due to unstable variations in parameters
For fig 5.15
This circuit is still of little practical value.
-
The base voltage Vx is always lower than the collector voltage.
-
For VA = : Voltage gain (w/o RE):
Requirements for active:
(w/ RE):
(w/ RE & RB):
Input Impedance (w/o RE):
(w/ RE):
(w/ RE & RB): Not including RB w/ Rin:
Including RB w/ Rin:
Output Impedance (w/o RE):
-
(w/ RE): Doesnt Change (w/ RE & RB): Doesnt Change
VA Voltage gain (w/o RE):
Input Impedance (w/o RE): Doesnt Change Output Impedance (w/o RE):
(w/ RE & not including RC):
(w/ RE & including RC):
w/o RE & w/o Voltage Divider-----------------------------------------------------------
Including RB:
------------------------------------------------------------------------------------
-
w/o RE, with Voltage Divider ------------------------------------------------------------
------------------------------------------------------------------------------------- w/ RE & Voltage Divider, w/o CRE --------------------------------------------------------
Va =
------------------------------------------------------------------------------------- w RE & Voltage Divider & CRE ------------------------------------------------------------
-------------------------------------------------------------------------------------
------------------------------------------------------------------------------------- General CE Stage
You can use Thevenin equivalents:
-
Small signal voltage gain (w/o Rs):
(w/ Rs):
(w/ RB & RE):
Voltage Headroom:
Input resistance (w/o RB):
(w/ RB):
Output Resistance (w/o RE on emitter):
(w/ RE on emitter):
(above: if RE is not RE1/gm), which also affects gain:
:
and
-
Small-signal volage gain
Input Impedance
Output Impedance
For Va
.
