Digital Electronics: Principles, Devices and Applications

Logic Families 1735.7.1 PMOS LogicThe PMOS logic family uses P-channel MOSFETS. Figure 5.57(a) shows an inverter circuit usingPMOS logic. MOSFET Q 1 acts as an active load for the MOSFET switch Q 2 . For the circuit shown,GND and −V DD respectively represent a logic ‘1’ and a logic ‘0’ for a positive logic system. Whenthe input is grounded (i.e. logic ‘1’), Q 2 remains in cut-off and −V DD appears at the output through-V DDQ1Y=AAQ 2(a)–V DDQ3——Y = (A+B)AQ 2BQ 1(b)Figure 5.57(a) PMOS logic inverter and (b) PMOS logic two-input NOR.