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, […]

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, […]

Phototransistor Working

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, […]

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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