Electronics (ECE) - MCQ Practice Questions

Clamping diodes protect circuits by limiting the maximum voltage that can be applied to a node. They conduct when voltage exceeds V_DD + V_D_forward or goes below V_SS - V_D_forward, preventing overstress to gate oxide and junctions.

Terminal voltage = Vz + Iz·Rz = 12 + (50×10^-3 × 5) = 12 + 0.25 = 12.25 V

When both junctions are forward biased, the transistor operates in saturation region where collector current is maximum and relatively independent of base current.

Photocurrent Iph = η·(q/hf)·Φ, where η is quantum efficiency and Φ is incident optical power.

The depletion region widens with more negative VGS, pinching off the channel and reducing ID until pinch-off voltage is reached.

For p-channel: |VGS - VT| = |-8 - (-2)| = |-6| = 6 V overdrive, or algebraically VGS - VT = -8 - (-2) = -6 V

Pconduction = ID²·RDS(on) = (20)²×0.5 = 400×0.5 = 200 W

GaAs has electron mobility ~8500 cm²/Vs, significantly higher than Si (~1350 cm²/Vs), enabling higher frequency operation.

Thermal voltage VT = kT/q, where k = 1.38×10⁻²³ J/K, T = 300K, q = 1.6×10⁻¹⁹ C. VT ≈ 26 mV at room temperature, a fundamental parameter in semiconductor device physics.