SEMICONDUCTOR DEVICES AND MICROELECTRONICS. Rica Paquio III- Galileo

Semiconductor Devices and Microelectronics Microelectronics DiodeJunction Diode Zener Diode Light Emitting Diode Photodiodes Other Diodes

Microelectronics  Microelectronics – the branch of electronics which deals with small miniaturized components.

Diodes  In electronics, a diode is a two-terminal electronic component with asymmetric conductance; it has low (ideally zero) resistance to current in one direction, and high (ideally infinite) resistance in the other.electronicsterminalelectronic componentconductanceresistancecurrentinfinite  A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–junction connected to two electrical terminalscrystallinesemiconductorp–junction

 Diodes are semiconductors components that allow current to flow in only one direction, from the positive (+) to the negative (-) side.

 When the Voltage on the positive leg is higher than on the negative leg then current flows through the diode ( the resistance is very low). The diode is said to be forward-biased.  When the Voltage is lower on the positive leg is higher than on the negative leg then current flow ( the resistance is very high ). The diode is said to be reverse-biased.

 The negative leg of a diode is the one with the line closest to it. It is called the cathode. The positive end is called anode. 

Junction Diode  The junction diode, like 1N4001, is the first type of diode developed. The name is derived from the principle of the diode, the positive-negative or p-n junction, hence the name.  To determine where the anode and cathode of a diode is, look for the white band on the diode. This is nearest to the cathode, or negative side.

 This diode has several types, based on the maximum current each can handle. Some diodes can handle u to 1A of current, others 3A, and so on. When buying this type of diode, get the current rating if it can handle the current that will pass through it.

Zener Diode  You might call this as a voltage reference diode. This is used to provide a certain voltage to a circuit, determined by the rating of the zener diode. If in junction diodes you have the current rating, in this diode, you have voltage, called the zener rating.

Light Emitting Diode  The Light Emitting Diode or LED is a special kind of diode. When current (around 10 to 40 mA) flows from the anode to the cathode, it lights up.  You can buy LEDs in small, medium, and large sizes (the bigger, the higher the current requirement), and in different colors like red, yellow, and green.  There are also infrared LEDs in the market where you cannot see light, some include microwave LEDs (like Gallium Arsenide or GaAs), while others are in the infrared range. This is paired with another diode, called photodiodes.

Photodiodes  A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. [1] If the anode and cathode leads of a photodiode are joined together by a wire, when in the dark, no current will flow. On the other hand, when in the light, current flows from the cathode to the anode.photodetectorlightcurrentvoltage [1]

 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.optical filterssolar cellsolar power

Photodiode operation

Other Diodes  Laser Diode: This type of diode is different from the LED type, as it produces coherent light. These diodes find their application in DVD and CD drives, laser pointers, etc. Laser diodes are more expensive than LEDs. However, they are cheaper than other forms of laser generators. Moreover, these laser diodes have limited life.

 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 Retification Version 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.convertsalternating currentdirect current  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.vacuum tubediodesmercury-arc valvessemiconductor diodessilicon- controlled rectifiers

Half-wave rectification[edit]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.single-phase supplythree-phase supply

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. center tappedtransformerbridge configuration

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.semiconductor deviceamplifyswitchelectronicelectrical powersemiconductorcurrentpoweramplifyintegrated circuits

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