ISCET Semiconductor Devices Questions and Answers

Question 1

A technician is building a simple voltage regulator circuit. Which semiconductor device is specifically designed to operate in the reverse breakdown region to maintain a constant voltage across its terminals?

Accepted Answer

Zener Diode

Answer

A Zener diode is engineered to have a precise and stable reverse breakdown voltage (Zener voltage). When reverse-biased at this voltage, it conducts current while maintaining a nearly constant voltage drop, making it ideal for voltage regulation applications.

Question 2

A technician needs to control a high-power AC load, such as a motor, using a low-power DC signal. Which three-terminal semiconductor device is most suitable for this application, acting as a latching switch?

Accepted Answer

Silicon-Controlled Rectifier (SCR)

Answer

A Silicon-Controlled Rectifier (SCR) is a type of thyristor designed to control large currents and voltages with a small gate current. Once triggered by a pulse to its gate, it 'latches' on and conducts current from anode to cathode until the current falls below a holding threshold, making it perfect for controlling AC power.

Question 3

When comparing a Bipolar Junction Transistor (BJT) to a Field-Effect Transistor (FET), which of the following is a key characteristic of the FET?

Accepted Answer

High input impedance

Answer

Field-Effect Transistors (FETs) are voltage-controlled devices and are characterized by their very high input impedance, typically in the megaohms range. This is because the gate terminal is insulated from the channel, drawing very little to no input current. BJTs, in contrast, are current-controlled and have a much lower input impedance.

Question 4

A technician is testing a standard silicon PN junction diode out of circuit using a digital multimeter's diode test function. What approximate voltage reading should the technician expect when the diode is forward-biased?

Accepted Answer

0.7 V

Answer

A standard silicon PN junction diode has a forward voltage drop of approximately 0.6V to 0.7V when it is conducting. The diode test function on a multimeter applies a small current and measures this voltage drop. A reading of 0.3V is typical for a germanium diode.

Question 5

In a semiconductor material, the process of intentionally adding impurities to increase its conductivity is known as:

Accepted Answer

Doping

Answer

Doping is the process of introducing impurity atoms into an intrinsic (pure) semiconductor crystal to change its electrical properties. Adding pentavalent impurities creates N-type material (excess electrons), while adding trivalent impurities creates P-type material (excess holes), both of which significantly increase conductivity.

(ISCET) International Society of Certified Electronics Technicians Practice Test

(ISCET) International Society of Certified Electronics Technicians Practice Test

ISCET Semiconductor Devices Questions and Answers