Industrial Power Electronics - Diodes

Question 1

A semiconductor substrate doped with arsenic (pentavalent) would be considered X-type semiconductor

Answer 1

N

Question 2

If the arsenic (N-type&pentavalent) was used in the constructionof a diode, what ‘lead designation’ would it be called?

Answer 2

Cathode (-)

Question 3

A photodiode is normally connected into a cct in X-bias; and as the illuminance is decreased, the diode’s resistance will X.

Answer 3

Reversed bias
Decrease, increase

Question 4

The forward current rating of an LED should not exceed XmA

Answer 4

50mA

Question 5

The PIV (Peak Inverse Voltage) rating of an LED is about Xvolts.

Answer 5

6V

Question 6

A clipper or surge suppressor cct ( to protect a load against peak voltage levels) can be constructed by using a device called a X

Answer 6

• Varistor
  What is the difference between a varistor and a resistor? But unlike a variable resistor whose resistance value can be manually varied between its minimum and maximum values, the varistor changes its resistance value automatically with the change in voltage across it making it a voltage-dependant, non-linear resistor or VDR for short.

-Thyrector

Question 7

Zener diodes are most commonly used in DC cct as a X?

Answer 7

Voltage regulator

Question 8

When a diode is connected across an inductive DC load (to protect arcing during switching operations), it is often called a X diode.

Answer 8

Free-wheeling

Freewheeling diode or flyback diode is a diode that is connected across an inductor to eliminate the flyback. Flyback is the sudden voltage spike that occurs across an inductive load due to interruption of supply current or sudden reduction. This voltage spike will damage the switches present in the circuits.

Question 9

Reverse-bias is a term to indicate that the anode is X with respect of the cathode

Answer 9

Negative

Question 10

Making the base of a NPN transistor more X will make it turn on less

Answer 10

Negative

Question 11

Making the base of PNP transistor more X will make it tuen on more

Answer 11

Negative

Question 12

The collector of a PNP transistor always has the same polarity as the (emitter or base ) lead

Answer 12

Base

Question 13

When the base emitter voltage of a silicon transistor has a value between 0 and 0,5V, normally the transistor is (on/off)

Answer 13

Off

Question 14

The arrow on the emitter symbol of a PNP transistor points towards the X potential (polarity)

Answer 14

Negative

Question 15

If the ‘base-to-emitter voltage for a transistor measures 3.6v, then this would probably indicate that the transistor is (normal/faulty)

Answer 15

Faulty

Question 16

The base-to-emitter for a silicon transistor measures 0,45v. This would normally indicate that the transistor is (on/off)

Answer 16

Off

Question 17

The collector-to-emitter voltage for a germanium transistor measures 0,07v. This would normally indicate that the transistor is (cut-off/saturated)

Answer 17

Saturated