Topic: Digital Circuits
In a CMOS inverter operating in the transition region, what best describes the operation of NMOS and PMOS transistors?
- A. Both are in cutoff region
- B. Only PMOS conducts
- C. Both are conducting
- D. Only NMOS conducts
Answer: C. Both are conducting
Explanation: During the transition region of a CMOS inverter (when the input voltage is approximately around $V_{DD}/2$), the input voltage is higher than the threshold voltage of the NMOS transistor and lower than $V_{DD} - |V_{tp}|$, which means both transistors are simultaneously turned ON and conducting. This leads to a momentary short-circuit (crowbar) current flowing directly from $V_{DD}$ to ground.