B.Sc. Engineering 1st Year: Basic Electronics Mid-Semester Exam

COE/EE 152: BASIC ELECTRONICS

Energy Level of Electrons

• Energy level of an electron: Electrons in the outermost shell have the highest energy level.

Linear Component

• Linear component: an increase in current is proportional to the applied voltage as given by Ohm's law.
• Example of a linear component: Resistor.

Semiconductor Material

• Doping material needed to make a p-type semiconductor material: trivalent.
• Doping material needed to make an n-type semiconductor material: pentavalent.

Diodes

• The point of intersection between the characteristic curve of the diode and the resistors loadline: Q-point or point of operation or quiescent point.
• Direction of the arrow in the diode symbol: from p-type of semiconductor to n-type semiconductor material.
• Reverse saturation current of a diode: doubles for every 10°C rise in the diode temperature.
• Effect of increasing temperature on a forward-biased diode: increases forward current.

Diode Testing

• Testing a diode with an ohmmeter: check its resistance in the forward and reverse direction.
• Resistances of a diode: relatively low in the forward direction and relatively high in the reverse direction.

Zener Region

• Current in the Zener region: can increase a lot.
• Voltage across the diode in the Zener region: is almost constant.

Light-Emitting Diodes

• Conditions for light emission in a p-n junction: forward-biased.

Semiconductor Devices

• Advantage of miniaturization: they operate more efficiently.
• Container purpose: provide a means for physical handling.

Capacitance

• Diffusion capacitance: a shunt capacitance effect that occurs when the diode is forward-biased.
• Transition capacitance: a shunt capacitive effect that occurs when the diode is reverse-biased.

Semiconductor Materials

• Two most common semiconductor materials: Silicon and Germanium.

Doping

• Doping: the process of adding impurities to pure semiconductor material.
• Effect of trivalent impurities: cause holes to be the majority carriers.
• Effect of pentavalent impurities: cause electrons to be the majority carriers.

Diode Equivalent

• Device roughly equivalent to a diode: a one-way valve.

Depletion Region

• Depletion region: acts as an insulator and the dielectric value is proportional to barrier potential.
• Effect of reverse bias on the depletion region: it increases.

Forward-Biased Diode

• A conducting forward-biased diode: behaves like a short circuit.

Rectifier Circuits

• DC Voltage on the load: depends on the voltage drop across the diodes.
• DC power supplied to the load: depends on the voltage drop across the diodes and the load resistance.
• Conversion efficiency of a rectifier: depends on the AC voltage, DC voltage, and power supplied.
• Peak value of the AC current: depends on the load resistance and the AC voltage.
• RMS value of the current supplied to the circuit: depends on the load resistance and the AC voltage.
• AC power supplied to the whole circuit: depends on the voltage and current.

Mid-semester exam questions for B.Sc. Engineering 1st year students at Kwame Nkrumah University of Science and Technology, covering basic electronics topics.