Revision: Electronic Components/ Study of Components and Circuits Computer Science 2 HSC Science (Computer Science) 11th Standard Maharashtra State Board

The reverse voltage at which the current suddenly increases rapidly is called the breakdown voltage.

The ratio of voltage to current at any operating point of a diode is called static resistance.

The ratio of a small change in voltage to the corresponding small change in current is called dynamic resistance.

The boundary formed when p-type and n-type semiconductor regions are joined in a single crystal is called a p-n junction.

The region around the junction that is free from mobile charge carriers is called the depletion region.

The potential difference developed across the depletion layer due to immobile ions is called the barrier potential.

The two-terminal semiconductor device that allows current mainly in one direction is called a p-n junction diode.

The process in which charge carriers move from a higher concentration to a lower concentration is called diffusion.

The motion of charge carriers under the influence of an electric field is called drift.

The minimum forward voltage after which the current rises sharply is called the knee voltage.

The small current flowing in reverse bias due to minority carriers is called the reverse saturation current.

• A rectifier that consists of one p-n junction diode in which alternate pulses of AC input are rectified, having a maximum efficiency of 40.6% and output frequency the same as that of input, is called a Half-Wave Rectifier.
• A rectifier which rectifies only one-half of each AC input supply cycle is called a half-wave rectifier.

R = \[\frac {V}{I}\]

\[r_d=\frac{\Delta V}{\Delta I}\]

• Size & Weight: Semiconductor devices are smaller in size and lightweight, which also enables faster speed of operation.
• Power Consumption: They operate at small voltages (few mV) and require very less current (µA or mA), hence consume lesser power and produce almost no heating effects — making them thermally stable.
• Controllability: The electronic properties of semiconductors can be controlled to suit our requirement, and fabrication of ICs is possible.
• Sensitivity: They are sensitive to electrostatic charges, radiation, and fluctuations in temperature — making them fragile in harsh environments.
• Limitations: They are not useful for controlling high power, require controlled conditions for manufacturing, and very few materials are semiconductors.

• A p-n junction is formed by joining p-type and n-type semiconductor regions in a single crystal.
• Diffusion of carriers creates a depletion region and barrier potential.
• A p-n junction diode conducts mainly in one direction.
• In forward bias, the barrier potential decreases, and the current becomes large.
• In reverse bias, the barrier potential increases and only a small minority-carrier current flows.
• In zero bias, the diffusion and drift currents balance, so the net current is zero.
• The knee voltage is about 0.3 V for germanium and 0.7 V for silicon.
• Static resistance is given by R = V/I, and dynamic resistance is given by r_d = ΔV/ΔI.

• A half-wave rectifier uses a single diode, allowing current to flow in one direction, with an AC power source\[V_{ac}\] connected to the diode and a resistor in series.
• Output is discontinuous and pulsating DC - only positive half cycles appear across the load.
• Alternative (negative) half cycles of the AC supply go to waste, making efficiency very low.
• The output waveform shows only the positive side of the sinusoidal cycle, clamping off the negative side.
• Circuit components: transformer (primary & secondary), single diode, and load resistor \[R_L\].
• A transformer is used to step up or step down the AC voltage before rectification.