1. Microelectronic Circuit Design, 3E McGraw-Hill Chapter 13 Small-Signal Modeling and Linear Amplification Microelectronic Circuit Design Richard C. Jaeger Travis N. Blalock

2. Jaeger/Blalock 7/20/07 Microelectronic Circuit Design, 3E McGraw-Hill Small-Signal Model of BJT Using 2-port y-parameter network, The port variables can represent either time-varying part of total voltages and currents or small changes in them away from Q-point values.  o is the small-signal common- emitter current gain of the BJT.

3. Jaeger/Blalock 7/20/07 Microelectronic Circuit Design, 3E McGraw-Hill Hybrid-Pi Model of BJT The hybrid-pi small-signal model is the intrinsic representation of the BJT. Small-signal parameters are controlled by the Q-point and are independent of geometry of the BJT Transconductance: Input resistance: Output resistance:

4. Jaeger/Blalock 7/20/07 Microelectronic Circuit Design, 3E McGraw-Hill Equivalent Forms of Small-Signal Model for BJT Voltage -controlled current source g m v be can be transformed into current-controlled current source, Basic relationship i c =  i b is useful in both dc and ac analysis when BJT is in forward-active region.

5. Microelectronic Circuit Design, 3E McGraw-Hill Small-Signal Model for the MOSFET Using 2-port y-parameter network, The port variables can represent either time-varying part of total voltages and currents or small changes in them away from Q-point values.

6. Microelectronic Circuit Design, 3E McGraw-Hill Small-Signal Parameters of MOSFET Since gate is insulated from channel by gate-oxide input resistance of transistor is infinite. Small-signal parameters are controlled by the Q-point. For same operating point, MOSFET has higher transconductance and lower output resistance that BJT. Transconductance: Output resistance: Amplification factor for V DS <<1: