Semi-conductor Devices and Circuits Essay Example | Topics and Well Written Essays - 5000 words

Semi-conductor Devices and Circuits - Essay Example The other terminal of the secondary transformer provides the negative. The load is cut across by the resistor. Figure 2 Voltage and current waveform of a half-wave rectifier Voltage relationship The half-wave rectifier states that the load voltage vL is Vdc and expressed in the following diagram. The load voltage is equal to 0 and the angular frequency of the source is w = 2? = T. This is expressed in the following diagram. From the diagram above, we can get the half-wave: Half-wave Vdc = Vm = 0.318Vm ? I.2 Full-wave rectification The full-wave rectification can be produced in two types: the center-tapped and the bridge rectification. I.2.1 The full-wave center-tapped The full-wave with center-tapped transformer has two diodes acting as half-wave rectifiers and whose negative ends are connected to the two terminals of the transformer secondary. The two diodes provide a full-wave output. The DC currents of the two half-wave rectifier diodes are equal and opposite. (Lee & Chow 2011, p. 150) Figure 3 Schematic diagram of full-wave rectification with center-tapped transformer secondary I.2.2 The bridge rectifier The bridge rectification uses four diodes to provide full-wave rectification, and this does not use a center-tapped transformer. The bridge rectification uses four diodes to provide full-wave rectification, and this does not use a center-tapped transformer. The rectification is done in such a way that the current flows D3 and D4, conduct when the negative half-cycle.... The positive and negative half-cycles of a full-wave rectifier are expressed in the following formula. The full-wave is: Vdc = 2Vm = 0.636Vm ? I.3 Zener regulator Most application of zener diode is as shunt voltage regulator; its specific role is to regulate the load voltage. There are various uses or applications for a zener diode, such as: 1. Voltage regulating element in voltage regulators 2. Protector in a circuit 3. Zener or voltage limiter Figure 5 The application of zener diode in a regulator circuit is shown in the figure below. In this circuit, zener diode is used as shunt regulator. The zener diode compensates for the variation in load current; the zener drifts with the temperature. The drift characteristics are given in many zener diode datasheets. Its load regulation is adequate for most supply specifications for integrated circuits. It has a higher loss than the series-pass type of linear regulator because its loss is set for the maximum load current. The zener shunt reg ulator uses a simple formula where input voltage is greater than output voltage; the output is controlled by the zener diode. The zener shunt regulator is typically used for very local voltage regulation for less than 200mW of a load. A series resistance is placed between a higher voltage and is used to limit the current to the load and zener diode. I.4 Switching and amplifier circuits for transistors An ordinary transistor has three terminals for the base, emitter and collector. When it is in the OFF position, the output comes from the collector of a common-emitter stage. A digital circuit usually operates in two modes. (The transistor amplifier n.d.) Transistors are used for switching and amplifiers in circuits. In digital logic, transistors have the ability to switch