Terminal Impedances

Eq. 5.162Eq. 5.198Eq. 5.291

BJT & MOS Transistor

[Chapter 4,5]

[Chapter 6,7]

Analogous Devices

• Terminals– “C”↔”D”– “E” ↔”S”– “B” ↔”G”

• Analogous Devices– NPN ↔NMOS– PNP ↔PMOS

Equivalent Circuit

Small Signal Model

Observations:1.Both Q1 and Q2 are represented by the SAME small signal circuit.2.To find the output resistance, find the terminal resistance by applyinga test voltage.

Big Picture

A Crude Metal Oxide Semiconductor (MOS) Device

P-Type Silicon is slightly conductive.

Positive charge attractnegative chargesto interface between insulator and silicon.

A conductive path is createdIf the density of electrons is sufficiently high.Q=CV.

V2 causes movement of negative charges,thus current.

V1 can control the resistivity of the channel.The gate

draws no current!

Resistance into the Base/Gate

Analogous Circuits

Three Derivations

Eq. 5.162 Eq. 5.198 Eq. 5.291