Paper 2 Semiconductors and Diodes Drills

Q1 Diode I-V Characteristic

1. Describe the current in reverse bias. [1]
2. Describe how current changes in forward bias after the threshold region. [2]
3. Explain why a diode is not an ohmic resistor. [2]

Q2 Sensor Potential Divider

A $6.0\mathrm{V}$ supply is connected to a fixed $4.0\mathrm{k\Omega }$ resistor in series with an NTC thermistor. The output is measured across the thermistor. At $20^{\circ }\mathrm{C}$, thermistor resistance is $6.0\mathrm{k\Omega }$.

1. Calculate $V_{out}$. [2]
2. State how $V_{out}$ changes when temperature increases. [2]
3. Explain why resistance trend alone is not enough unless output position is known. [2]

Q3 Half-Wave Rectification

1. Explain how one diode produces half-wave rectification. [2]
2. State why the output is pulsating dc rather than steady dc. [2]