Voltage transfer characteristics

The voltage transfer characteristics can be obtained by superimposing current characteristics of NMOS and PMOS devices.This is called a load-line plot.

Idsp = -Idsn
Vgsn =Vin; Vgsp = Vin -Vdd
Vdsn = Vout ; Vdsp = Vout - Vdd

• The VTC of the inverter hence exhibits a very narrow transition zone. This results fromthe high gain during the switching transient, when both NMOS and PMOS are simultaneously on, and in saturation. In that operation region, a small change in the input voltage results in a large output variation