积体电路概论.pptVIP

Chapter 02Logic Design with MOSFETs Outline The Fundamental MOSFETs Ideal Switches and Boolean Operations MOSFETs as Switches Basic Logic Gates in CMOS Complex Logic Gates in CMOS Transmission Gate Circuits Clocking and Dataflow Control p-n Junction A junction between p-type and n-type semiconductor forms a diode Current flows only in one direction nMOS Transistor Four terminals: gate (G), source (S), drain (D), body (B) Gate–oxide–body stack looks like a capacitor Gate and body are conductors SiO2 (oxide) is a very good insulator Called metal – oxide – semiconductor (MOS) capacitor Even though gate is no longer made of metal nMOS Operation (1/2) Body is usually tied to ground (0 V) When the gate is at a low voltage P-type body is at low voltage Source-body and drain-body diodes are OFF No current flows, transistor is OFF nMOS Operation (2/2) When the gate is at a high voltage Positive charge on gate of MOS capacitor Negative charge attracted to body Inverts a channel under gate to n-type Now current can flow through n-type silicon from source through channel to drain, transistor is ON pMOS Transistor Similar, but doping and voltages reversed Body tied to high voltage (VDD) Gate “low”: transistor ON Gate “high”: transistor OFF Bubble indicates inverted behavior Outline The Fundamental MOSFETs Ideal Switches and Boolean Operations MOSFETs as Switches Basic Logic Gates in CMOS Complex Logic Gates in CMOS Transmission Gate Circuits Clocking and Dataflow Control Ideal Switches (1/3) Ideal Switches (2/3) Ideal Switches (3/3) Outline The Fundamental MOSFETs Ideal Switches and Boolean Operations MOSFETs as Switches Basic Logic Gates in CMOS Complex Logic Gates in CMOS Transmission Gate Circuits Clocking and Dataflow Control MOSFET as Switches MOSFET as Switches Early generations of silicon MOS logic circuits used both positive and negative supply voltages as Figure 2.10 showing In modern designs require only a single positive voltage VDD and the ground connectio