Electronic Devices and Circuits

Tunnel Diode Operation and Characteristics

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

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

Voltage Variable Capacitors: VVC Operation – Voltage Variable Capacitors diodes (VVCs) are also known as vari¬≠caps, 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

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

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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Photodiode Operation and Characteristics

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: 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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