JFET Construction and Working The junction field-effect transistor (JFET) is a three element electronic device. Its operation is based on the conduction of current carriers through a single piece of semiconductor material. This piece of material is called the channel. An additional piece of semiconductor material is diffused into the channel. This element is called […]
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Power MOSFET Construction and Working Metal-oxide semiconductor field-effect transistors (MOSFETs) are a rather new addition to the unipolar transistor family. A distinguishing feature of this device is its gate construction. The gate is, for example, completely insulated from the channel. Voltage applied to the gate will cause it to develop an electrostatic charge. No current
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Light Sensitive Devices Light-sensitive devices include photo cells, solar cells, photo-diodes, and photo-transistors. Photo Cell It is a light-sensitive device in which the internal resistance changes with a change in light intensity. The resistance change is not proportional to the light striking it. The photo cell is made from light-sensitive material such as cadmium sulfide
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There are two categories of SCR, the fast turn-off inverter grade SCR and relatively slow turn-off converter grade SCR. Some of the properties of these are interdependent and designers have aimed to combine them in most suitable manner. The application therefore decides what category is to be chosen. Once the category is chosen in each
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The bipolar junction transistor is a current-controlled device, while the field-effect transistor (FET) is a voltage-controlled device. The field-effect transistor uses basically no input current. Instead, output current flow is controlled by a varying electric field, which is created through the application of a voltage. This is the origin of the term field effect. The
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Operational amplifiers (op-amps) are analog circuit components that require power to operate. They are widely used in amplification and signal-conditioning circuits. The symbol for an op-amp is shown in Figure 1. The symbol is a triangle, with two leads drawn on one side of the triangle, and the third lead is drawn at the apex
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The 555 timer chip (such as the NE555 8-pin chip from Texas Instruments) is an integrated circuit that uses a transistor, resistors, flip-flops, comparators, and capacitors to produce a variety of clock signals, including a fixed pulse, a periodic signal, and a frequency dividing signal. The NE555 can operate over a wide voltage supply range
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A SCR (silicon-controlled rectifier) is a three-terminal semiconductor device that behaves like a diode but with an additional terminal. The additional terminal is called a gate, and when a small current flows into the gate, it allows a much larger current to flow from the anode to the cathode (provided that the voltage between the
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Metal-oxide semiconductor field effect transistors (MOSFETs) are the other family of transistors that are commonly used. The MOSFET is based on the original field effect transistor (FET) that was introduced in the 1960s. Similar to the BJT family, they are also three terminal devices, but they have different names for the terminals, and they operate
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An ideal dc voltage source produces a load voltage that is constant. The simplest example of an ideal dc voltage source is a perfect battery, one whose internal resistance is zero. Figure 1(a) shows an ideal voltage source connected to a variable load resistance of 1 V to 10 MΩ. The voltmeter reads 10 V,
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