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CMOS Inverter and Logic Gates — MCQs – EE

1. The term CMOS stands for:

(A) Complementary Metal Oxide Semiconductor


(B) Combined Metal Oxide Semiconductor


(C) Controlled Metal Oxide Semiconductor


(D) Composite Metal Oxide Semiconductor



2. A CMOS inverter consists of:

(A) One NMOS and one PMOS transistor


(B) Two NMOS transistors


(C) Two PMOS transistors


(D) One BJT and one MOSFET



3. In a CMOS inverter, when the input is low, the output is:

(A) High


(B) Low


(C) Floating


(D) Undefined



4. In a CMOS inverter, when the input is high, the output is:

(A) Low


(B) High


(C) Zero current


(D) Same as input



5. The PMOS transistor in a CMOS inverter conducts when the input is:

(A) Low


(B) High


(C) Floating


(D) Undefined



6. The NMOS transistor in a CMOS inverter conducts when the input is:

(A) High


(B) Low


(C) Zero


(D) Floating



7. The main advantage of CMOS logic is:

(A) Very low static power dissipation


(B) High static power dissipation


(C) High noise generation


(D) Low switching speed



8. The output of a CMOS inverter is ideally:

(A) The complement of the input


(B) Equal to the input


(C) Always zero


(D) Always one



9. The switching point of a CMOS inverter depends on:

(A) The ratio of NMOS and PMOS sizes


(B) Supply voltage only


(C) Frequency of operation


(D) Load capacitance only



10. The voltage transfer characteristic (VTC) of a CMOS inverter has:

(A) A sharp transition region


(B) A linear response


(C) A constant output


(D) Multiple peaks



11. The static power consumption in CMOS occurs primarily due to:

(A) Leakage currents


(B) Short-circuit current


(C) Resistive heating


(D) Switching loss



12. Dynamic power dissipation in CMOS circuits is mainly due to:

(A) Charging and discharging of load capacitances


(B) Reverse leakage current


(C) Forward conduction loss


(D) Breakdown voltage



13. The propagation delay in CMOS inverter increases with:

(A) Load capacitance


(B) Supply voltage


(C) Channel mobility


(D) Shorter channel length



14. The noise margin of a CMOS inverter is:

(A) High


(B) Low


(C) Zero


(D) Undefined



15. CMOS logic gates are preferred because they offer:

(A) High noise immunity and low power


(B) Low noise and high power


(C) Low switching speed


(D) High static current



16. The basic logic gates built using CMOS are:

(A) NOT, NAND, NOR


(B) AND, OR only


(C) XOR, XNOR only


(D) Flip-flops only



17. A CMOS NAND gate conducts to logic low output when:

(A) All inputs are high


(B) All inputs are low


(C) One input is low


(D) Both inputs are floating



18. A CMOS NOR gate conducts to logic high output when:

(A) All inputs are low


(B) Any input is high


(C) One input is floating


(D) All inputs are high



19. In a CMOS NAND gate, the NMOS transistors are connected in:

(A) Series


(B) Parallel


(C) Cross-coupled


(D) Cascaded



20. In a CMOS NOR gate, the PMOS transistors are connected in:

(A) Series


(B) Parallel


(C) Cascaded


(D) Differential pair



21. In CMOS logic, fan-out refers to:

(A) The number of inputs driven by a single output


(B) The output voltage level


(C) The number of transistors


(D) The gate capacitance



22. The main limitation of CMOS technology is:

(A) Sensitivity to static discharge


(B) High static power


(C) Low integration density


(D) Poor speed performance



23. The complementary operation of CMOS means:

(A) PMOS and NMOS are never ON simultaneously


(B) PMOS and NMOS always ON together


(C) Only PMOS conducts


(D) Both transistors always OFF



24. A logic ‘1’ at the output of a CMOS inverter corresponds to:

(A) Supply voltage (VDD)


(B) Ground


(C) Half of VDD


(D) Floating potential



25. A logic ‘0’ at the output of a CMOS inverter corresponds to:

(A) Ground (0V)


(B) Supply voltage (VDD)


(C) Half of VDD


(D) Undefined voltage



26. The short-circuit current in CMOS occurs during:

(A) Switching transition


(B) Static operation


(C) Power-down mode


(D) Idle state



27. The complementary action in CMOS gates ensures:

(A) Very low static current


(B) High static current


(C) High input capacitance


(D) Constant current operation



28. A CMOS inverter provides the basic building block for:

(A) All CMOS logic gates


(B) Only flip-flops


(C) Only amplifiers


(D) Power circuits



29. The output impedance of a CMOS inverter in steady states is:

(A) Very low


(B) Very high


(C) Moderate


(D) Infinite



30. The switching threshold of a CMOS inverter ideally lies:

(A) Near half of the supply voltage


(B) At zero volts


(C) Near the supply voltage


(D) Undefined



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