SEMICONDUCTOR DEVICES AND MICROELECTRONICS.Rica Paquio III- Galileo

Semiconductor Devices and Microelectronics

Microelectronics

Diode Junction Diode

Zener Diode

Light Emitting Diode

Photodiodes Other Diodes

Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as its surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode.

Photodiode operation

Small signal or Small current diode - These diodes assumes that the operating point is not affected because the signal is small

  Large signal diodes - The operating point in these diodes get affected as the signal is large.

Transient voltage supression diodes - This diode is used to protect the electronics that are sensitive against voltage spikes.

Diode Application

Rectification ("frequency shifting") Typical power supply

applications

Half-Wave Rectification

"Figure shows a half-wave rectifier circuit. The signal is exactly the top half of the input voltage signal, and for an ideal diode does not depend at all on the size of the load resistor.

"The rectified signal is now a combination of an AC signal and a DC component.  Generally, it is the DC part of a rectified signal that is of interest, and the un-welcomed AC component is described as ripple. It is desirable to move the ripple to high frequencies where it is easier to remove by a low-pass filter."When diodes are used in small-signal applications - a few volts - their behaviour is not closely approximated by the ideal model because of the PN turn-on voltage. The equivalent circuit model can be used to evaluate the detailed action of the rectifier under these conditions.

During the part of the wave when the input is positive but less than the PN turn-on voltage, the model predicts no loop current and the output signal voltage is therefore zero. When the input exceeds this voltage, the output signal becomes proportional to, or about 0.6 V lower than the source voltage."

Full-Wave RetificationVersion 1 - Center-Tap Full-Wave Rectifier

Version 2 - Bridge Full-Wave Rectifier

"The diode bridge circuit shown Ö is a full-wave rectifier. The diodes act to route the current from both halves of the AC wave through the load resistor in the same direction, and the voltage developed across the load resistor becomes the rectified output signal. The diode bridge is a commonly used circuit and is available as a four-terminal component in a number of different power and voltage ratings."

Rectification

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.

The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches.

Half-wave rectification[edit]

In half wave rectification of a single-phase supply, either the positive or negative half of the AC wave is passed, while the other half is blocked. Because only one half of the input waveform reaches the output, mean voltage is lower. Half-wave rectification requires a single diode in a single-phase supply, or three in a three-phase supply. Rectifiers yield a unidirectional but pulsating direct current; half-wave rectifiers produce far more ripple than full-wave rectifiers, and much more filtering is needed to eliminate harmonics of the AC frequency from the output.

Full-wave rectification

A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Full-wave rectification converts both polarities of the input waveform to pulsating DC (direct current), and yields a higher average output voltage. Two diodes and a center tappedtransformer, or four diodes in a bridge configuration and any AC source (including a transformer without center tap), are needed. 

Transitor

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage orcurrent applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

(Assorted discrete transistors. Packages in order from top to bottom: TO-3, TO-126, TO-92,SOT-23)