- re transistor model – employs a diode and controlled current source to duplicate the behavior of a transistor in the region of interest.
- The re and hybrid models will be used to analyze small-signal AC analysis of standard transistor network configurations.
- The network analyzed represent the majority of those appearing in practice today.
- Setting all DC sources to zero
- Replacing all capacitors by s/c equiv.
- Redraw the network in more convenient and logical form
Common-Emitter (CE) Fixed-Bias Configuration
The Common-Emitter is characterized as having high input impedance and low output impedance with a high voltage and current gain.
Removing DC effects of VCC and Capacitors
The negative sign used in the voltage gain formulas indicates the inversion.
CE – Voltage-Divider Bias Configuration
Common-Base (CB) Configuration
The Common-Base is characterized as having low input impedance and high output impedance with a current gain less than 1 and a very high voltage gain.
hfe = b hfb = -a
hoe = 1/ro