Tunnel Diode Parallel Amplifier Circuit: For operation as an amplifier, a tunnel diode must be biased to the center of its negative resistance region. Figure 21-17(a) shows the basic circuit of a Tunnel Diode Parallel Amplifier Circuit. Load resistor RL is connected in parallel with diode D1 and supplied with current from voltage source EB […]
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Tunnel Diode Operation and Characteristics: Tunnel Diode Operation – A tunnel diode (sometimes called an Esaki diode after its inventor, Leo Esaki) is a two-terminal negative resistance device that can be employed as an amplifier, an oscillator, or a switch. Recall from earlier topics that the width of the depletion region at a pn-junction depends
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Thermistor Operation: 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 (NTC), but positive temperature coefficient (PTC) devices are also available. Thermistor Operation are widely applied for measurement and control of temperature, liquid, level, gas flow, etc. Silicon
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Voltage Variable Capacitors: VVC Operation – Voltage Variable Capacitors diodes (VVCs) are also known as varicaps, varactors, and as tuning diodes. Basically, a Voltage Variable Capacitors is a reverse biased diode, and its capacitance is the junction capacitance. Recall that the width of the depletion region at a pn-junction depends upon the reverse bias voltage,
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Optocoupler Circuit Operation: An Optocoupler Circuit Operation (optoelectronic coupler) is essentially a photo-transistor and an LED combined in one package. Figure 20-35(a) and (b) shows the typical circuit and terminal arrangement for one such device contained in a DIL plastic package. When current flows in the LED, the emitted light is directed to the phototransistor,
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Photodarlington Working: The Photodarlington Working shown in (Fig. 20-33) consists of a phototransistor connected in Darlington arrangement with another transistor. This device is capable of producing much higher output currents than a phototransistor, and so it has a greater sensitivity to illumination levels than either a phototransistor or a photodiode. With the additional transistor involved,
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Phototransistor Working: A Phototransistor Working is similar to an ordinary BJT except that its collector base junction is constructed like a photodiode. Instead of a base current, the input to the transistor is in the form of illumination at the junction. Construction and Working of Phototransistor: Consider an ordinary BJT with its base terminal open-circuited,
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Solar Energy Conversion Diagram: The Solar Energy Conversion Diagram, or solar energy converter, is essentially a large photodiode designed to operate solely as a photovoltaic device and to give as much output power as possible. To provide maximum output current, solar cell surface areas are much larger than those of signal photodiodes, Typical solar cell
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Photodiode Operation and Characteristics: Photodiode Operation – When a pn-Junction is reverse biased, a small reverse saturation current flows due to thermally generated holes and electrons being swept across the junction as minority charge carriers. Increasing the junction temperature generates more hole-electron pairs, and so the minority carrier (reverse) current is increased. The same effect
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Photoconductive Cell Construction and Working: Photoconductive Cell Construction and Working – Light striking the surface of a material can provide sufficient energy to cause electrons within the material to break away from their atoms. Thus, free electrons and holes (charge carriers) are created within the material, and consequently its resistance is reduced. This is known
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