Transistor Action : Operation of PNP Transistor: Transistor action – Transistors of both types (P-N-P and N-P-N) behave exactly in the same way except change in biasing and majority carriers. In P-N-P transistors the conduction is by holes whereas in N-P-N transistors conduction is by electrons. However, N-P-N transistors are preferred due to their better […]
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Transistor Terminals (Emitter, Collector and Base): As mentioned already, transistor is a single crystal in which there are two P-N junctions, as shown in Fig. 10.1. The idea behind is to have first section to supply the charges (either holes or electrons) to be collected by the third section through the middle section. One side
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Transistor Construction: The transistor construction consists of a silicon or germanium (preferably silicon because of its smaller cutoff current ICBO, smaller variations in ICBO due to variations in temperature and higher operating temperature) crystal in which a layer of N-type material is sandwiched between two layers of P-type material, as shown in Fig. 10.1 (a). Alternatively
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Three Phase Rectifiers: Three-Phase Half-Wave Rectifier : Figure 9.11 illustrates a circuit for a 3-phase half-wave rectifier. The three diodes are connected to the three phases of a 3-phase transformer star-connected secondary. Neutral point N of the secondary forms the negative terminal for the load and is earthed, as illustrated in Fig. 9.11. Input and
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Voltage Multipliers – Voltage Doublers, Triplers and Quadruplers Voltage multipliers is a modified capacitor filter circuit that delivers a dc voltage twice or more times of the peak value (amplitude) of the input ac voltage. Such power supplies are used for high-voltage and low-current devices such as cathode-ray tubes (the picture tubes in TV receivers,
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What is Bleeder Resistor? – Working and Its Functions The operation of an inductor filter is based on the fact that a minimum current flows through it at all times. To provide flow of this minimum current at all times through the choke, a resistor called the bleeder resistor is placed across the filter output,
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What is Surge Current? – Definition and Workings Before switching on of power supply, the filter capacitor is uncharged [Fig. 9.23]. At the instant the power supply is switched on, the uncharged capacitor behaves like a short, and therefore, the initial charging current may be quite large. In the worst case, the circuit may be
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Baritt diode – Working and Applications: The barrier-inject transit time (BARITT) diode is basically a back-to-back pair of diodes biased into reach-through condition. It belongs to the transit-time microwave diode family. In this diode microwave oscillation occurs due to the thermionic injection and diffusion of minority carriers across the forward-biased barrier and a 3π/2 transit
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What is a thermistor? – Definition, Symbol and V-I Characteristics: The word thermistor is a combination of thermal and resistor. A thermistor is a resistor with definite thermal characteristics. Most thermistors have a negative temperature coefficient, but positive temperature coefficient devices are also available. The reason of negative temperature coefficient of resistance of a semiconductor
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Varistors or Voltage Dependent Resistors (VDRS): Varistors, also called the voltage dependent resistors (VDRs), show a high degree of nonlinearity between their resistance value and the applied voltage. They are made of non-homogeneous materials giving a rectifying action at the contact of two particles. Various materials, such as silicon carbide, zinc oxide, are used to
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