In CMOS technology, which transistors are used to form the electrically controlled gate?

• A. Only N-type transistors
• B. Only P-type transistors
• C. Both N-type and P-type transistors
• D. Neither

Answer: (C)

In CMOS logic, both N-type and P-type transistors are used to form the gate. The input controls a complementary pair: when the input is high, the NMOS turns on and pulls the output toward ground; when the input is low, the PMOS turns on and pulls the output up to Vdd. This arrangement gives a strong, full-range output and minimal static power consumption because, at any steady state, only one path conducts. Relying on a single type would either fail to drive the output cleanly to the opposite rail or waste power, whereas using both types together provides efficient, rail-to-rail switching.