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 […]
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
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
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
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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Figure 1(a) shows a boost converter, another basic topology for converters. A boost converter always steps the voltage up. The theory of operation is similar to that for a buck converter in some ways but very different in others. Boost Converter Working For instance, when the pulse is high, the switch is closed and energy
Figure 1(a) shows a buck converter, the most basic topology for converters. A buck converter always steps the voltage down. A transistor, either a bipolar junction or a power FET, is used as the switching device. A rectangular signal out of the pulse-width modulator closes and opens the switch. A comparator controls the duty cycle
This article covers the following items about electrical timers: The five sections of timers Nine timer operating principles Five common modes of timer operations Timer charts Sections of Electrical Timer Figure 1 provides a block diagram that shows the five functional sections of a timer. Timers can be divided into the following sections: Power or
When a high reverse-biased voltage applied to a diode may create a high reverse current, which can generate excessive heat and cause a diode to break down. The applied reverse voltage at which the breakdown occurs is called the breakdown voltage, or peak reverse voltage. A special diode called a zener diode is connected to
There are two types of extrinsic semiconductors. These are n-type and p-type. In n-type, the electrons are majority charge carriers while holes are minority charge carriers. In p-type, the holes are majority charge carriers and electrons are minority charge carriers. When these two types of materials namely n-type and p-type are chemically combined with a special