Semiconductor Devices Physics - Semiconductor Devices

A logic gate is an electronic circuit which

Solar cell operates on the principle of

An LED emits visible light when its

A series resistance is connected in the Zener diode circuit to

In a BJT, the largest current flow occurs

Which method of biasing is used for operating transistor as an amplifier?

In a comman-base connection, a certain transistor has an emitter current of 10mA and collector current of 9.8 mA. Calculate the value of the base current.

When the intensity of light incident on a photo diode increases, how is the reverse current affected?

A full wave rectifier utilises both half cycles of AC input voltage to produce the DC output.

The common-base DC current gain of a transistor is 0.967. If the emitter current is 10mA. What is the value of base current?

What is the difference between a photo diode and a solar cell?

The current rating of LED is of a few tens of milli-amps. Hence it is necessary to connect a high resistance in series with it. The forward voltage drop of an LED is much larger than an ordinary diode and is around 1.5 to 3.5 volts.

LED junction does not actually emit that much light so the epoxy resin body is constructed in such a way that the photons emitted by the junction are reflected away from the surrounding substrate base to which the diode is attached and are focused upwards through the domed top of the LED, which itself acts like a lens concentrating the light. This is why the emitted light appears to be brightest at the top of the LED.

The voltage stabilization is effective when there is a minimum Zener current. The Zener diode must be always operated within its breakdown region when there is a load connected in the circuit. Similarly, the supply voltage Vs must be greater than Vz.

Why do we need filters in a power supply?

What would happen if both junctions of a BJT are forward biased or reverse biased?

State the principle and uses of a solar Cell.

Why should a photodiode be operated in reverse biased mode?

White Light LEDs or White LED Lamps:
Shuji Nakamura, a Japanese – born American electronic engineer invented the blue LED. He was awarded the Nobel prize for physics for 2014. He was also awarded the global energy prize in the year 2015. His invention of blue LED made the fabrication of white LED possible.
LED lamps, bulbs, street lighting are becoming very popular these days because of the very high efficiency of LEDs in terms of light output per unit input power(in milliWatts), as compared to the incandescent bulbs. So for general purpose lightings, white light is preferred.
Commercially available white LEDs are normally manufactured by using the technique of wavelength conversion. It is a process which partly or completely converts the radiation of a LED into white light. There are many ways of wavelength conversion. One of these methods uses blue LED and yellow phosphor. In this method of wavelength conversion, a LED which emits blue colour is used to excite a yellow colour phosphor. This results in the emission of yellow and blue light and this mixture of blue and yellow light gives the appearance of white light. This method is the least expensive method for producing white light.

Why is a resistance connected in series with a Zener diode when used in a circuit?

How does a cell phone charger produce a voltage of 5.0 V form the line voltage of 230V?

Why is the emitter, the base and the collector of a BJT doped differently?