Ch 16Semiconductor Devices — Class 12 Physics, concept-first.

In Class XI we studied the p-n junction diode's basic switching behaviour: forward biased, it behaves like a closed switch and current flows; reverse biased, it behaves like an open switch and only a…

An AC voltage is bidirectional: its value and its direction of flow both keep changing, retracing the same sinusoidal pattern once every cycle.

The half wave rectifier is the simplest possible rectifier circuit, built from a single diode. A transformer's secondary coil (with its two ends labelled A and B) is connected in series with a diode D…

The half wave rectifier's fundamental weakness is that it throws away every negative half cycle of the input entirely, so its efficiency is very poor.

The output of a rectifier is never perfectly smooth DC -- it always retains a small leftover AC component riding on top of the intended steady DC level.

A rectifier's raw output -- whether half wave or full wave -- is unidirectional but still far from steady: it keeps fluctuating because of the ripple component present in it.

This section moves on from rectifier circuits to a set of SPECIAL PURPOSE JUNCTION DIODES -- p-n junction diodes deliberately designed and operated to exploit some particular electrical or optical pro…

This section studies several special-purpose junction diodes: the Zener diode, the photo diode, the solar cell, and the light-emitting diode (LED).

A PHOTODIODE is a special p-n junction diode designed to convert light energy directly into electrical energy -- it generates a current when exposed to light, which is why it is also called a photodet…

Solar energy can be harnessed in two broad ways: PHOTOTHERMAL devices, which convert solar energy into heat (mostly used for heating water), and PHOTOVOLTAIC devices, which convert solar energy direct…

The LIGHT EMITTING DIODE (LED) is a diode that emits light when a sufficiently large forward current is passed through it.

A junction transistor is a semiconductor device having TWO junctions and THREE terminals; because current in it is carried by both electrons and holes together, it is called a BIPOLAR JUNCTION TRANSIS…

The Common Emitter (CE) configuration -- in which the emitter terminal is shared between the input loop (base-emitter) and the output loop (collector-emitter), Fig.

Using the circuit of Fig. 16.22, two standard characteristic curves are measured for a transistor in the common emitter configuration. The INPUT CHARACTERISTIC (Fig.

An AMPLIFIER is a device that increases the amplitude of an alternating signal -- voltage, current, or power.

So far, the signals discussed in this course -- and in the previous class -- have been continuously varying (ANALOG) signals: a sinusoidal voltage, for instance, smoothly takes on every intermediate v…

The NOT gate is the most basic logic gate of all: it has exactly ONE input and ONE output, and simply produces the NEGATED (inverted) version of whatever is applied at its input -- if the input is 0 (…

The OR gate has two (or more) inputs and a single output, and represents what is sometimes called LOGICAL ADDITION.

The AND gate has two (or more) inputs and a single output, and represents LOGICAL MULTIPLICATION. Its output Y is 1 (high) ONLY when ALL of its inputs are simultaneously 1 (high) -- for the standard t…

The NAND gate is formed by connecting the output of an AND gate into the input of a NOT gate -- i.e. it is simply an AND gate followed by inversion -- and its name ('NOT-AND') reflects exactly this co…

The NOR gate is formed by connecting the output of an OR gate into the input of a NOT gate -- i.e. it is simply an OR gate followed by inversion -- and its output is therefore the exact OPPOSITE of a…

The Exclusive-OR (X-OR) gate is a two-input, one-output gate whose defining behaviour is that its output goes HIGH (1) only when its two inputs are at genuinely DIFFERENT logic levels from each other…

Sample papers and previous-year board questions for this subject.