Semiconductor Electronics

A solid has a forbidden energy gap of about 1.1 eV between its valence and conduction bands. How would this solid be classified at room temperature?

A semiconductor at a given temperature has an intrinsic carrier concentration n(i) = 1.5×10¹⁰ cm⁻³. After doping, the free electron concentration becomes n = 2.25×10¹³ cm⁻³. What is the hole concentration p?

Pure germanium (tetravalent) is doped with a small amount of phosphorus (pentavalent). What type of semiconductor results, and what is the majority carrier?

At room temperature, which has the larger barrier (junction) potential — a silicon p-n junction or a germanium p-n junction?

When a p-n junction diode is forward biased, what happens to the width of the depletion region and the height of the potential barrier?

In a reverse-biased p-n junction diode, the small reverse saturation current that does flow is carried mainly by which charge carriers?

A mains AC supply of frequency 50 Hz is fed into a full-wave (bridge) rectifier. What is the ripple frequency of the rectifier's output?

What is the maximum theoretical efficiency of a half-wave rectifier, and why is it well below 100%?

In a rectifier circuit fitted with a shunt capacitor filter, what happens to the output ripple if the load resistance is increased (capacitance unchanged)?

A Zener diode voltage regulator has an input voltage of 12 V, a series resistor of 100 Ω, and a Zener breakdown voltage of 6 V. If the load draws a constant current of 20 mA, what is the current flowing through the Zener diode itself?

For a device to function as an LED (light-emitting diode) or as a photodiode, in what bias mode is each normally operated respectively?

Why can a solar cell generate an EMF and deliver power to an external circuit without needing any battery or external bias at all?

A transistor has an emitter current of 10 mA and a base current of 0.1 mA. What are the collector current, the common-base current gain α, and the common-emitter current gain β?

A transistor has a common-base current gain α = 0.98. What is its approximate common-emitter current gain β?

A transistor has a common-emitter current gain β = 99. What is its approximate common-base current gain α?

A common-emitter amplifier has β = 50, a collector resistance R(C) = 2000 Ω, and an input (base) resistance R(in) = 500 Ω. What is its voltage gain?

For the amplifier in the previous question, what is its power gain? (Take current gain A(i) ≈ β)

A transistor used purely as an electronic switch is deliberately driven into cut-off and saturation, avoiding its active (linear) region. What characterises each of these two states?

A common-emitter amplifier's output voltage, for a sinusoidal input signal, is best described as:

Which of the following statements about logic gates is correct?