Characteristic curves of a p-n junction and a Zener diode — practice questions

Question 1 · difficulty L1 · recall

The forward characteristic of a p-n junction shows a rapid current rise after

• A. the knee voltage
• B. reverse breakdown only
• C. zero current at all voltages
• D. the Zener voltage in forward bias always

Question 2 · difficulty L1 · understanding

The reverse current of an ordinary diode before breakdown is

• A. larger than the forward current at the same voltage magnitude
• B. small
• C. infinite
• D. exactly equal to forward current

Question 3 · difficulty L2 · understanding

A Zener diode's regulation region appears on the I-V graph in

• A. forward-bias linear region only
• B. zero-bias point only
• C. reverse breakdown
• D. a region of no current and changing voltage

Question 4 · difficulty L2 · application

In plotting a diode characteristic, a series resistor is used mainly to

• A. make the diode perfectly ohmic
• B. remove the need for voltage measurement
• C. change the sign of charge carriers
• D. limit current and protect the diode

Question 5 · difficulty L3 · application

To plot the forward I-V curve accurately, the voltmeter should measure

• A. voltage directly across the diode
• B. only battery emf regardless of resistor drop
• C. current through the diode
• D. resistance of the ammeter

Question 6 · difficulty L3 · application

A diode curve shows about 0.7 V at a sharp forward-current rise. The device is most consistent with

• A. an ideal resistor
• B. a silicon diode
• C. a glass prism
• D. a galvanometer coil

Question 7 · difficulty L4 · analysis

On a Zener reverse characteristic, increasing current substantially while voltage changes only slightly indicates

• A. very large dynamic resistance
• B. no breakdown
• C. small dynamic resistance in breakdown
• D. forward open-circuit behaviour

Question 8 · difficulty L4 · analysis

If diode temperature rises, the forward voltage required for a given current in a silicon diode generally

• A. increases strongly
• B. stays exactly constant
• C. becomes equal to breakdown voltage
• D. decreases

Question 9 · difficulty L5 · analysis

Why should current and voltage readings be taken in small increments near a diode knee or Zener breakdown?

• A. The characteristic changes rapidly there
• B. The graph is perfectly linear there
• C. No current flows there
• D. Voltage meters stop working elsewhere

Question 10 · difficulty L5 · analysis

A plotted Zener curve shows reverse voltage clamped near 5.1 V across a broad current interval. In a regulator, this feature means output can remain near

• A. 0 V
• B. 5.1 V
• C. the entire supply voltage regardless of current limit
• D. 51 V