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|FIELD-EFFECT TRANSISTORS - FETS|
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FETs have a source, drain and gate, which are arranged in a similar way, to the ‘pins’ of a bipolar junction transistor (BJTs), such as an NPN or PNP transistor - collector, base and emitter.
The gate of a FET, plays a similar role as the base of a BJT. When the gate is triggered, it allows current to flow through the drain and source. However, it requires vary little current to trigger the gate, unlike BJTs.
|CLASSIFICATION OF COMMON FETs|
A variety of FETs are available - some are shown below.
JFET-Junction Field Effect Transistor
|The two circuits below include a N channel MOSFET. An input to the Gate, triggers the MOSFET, allowing current to flow through the Drain and Source, driving the motor the and buzzer.|
|The temperature sensor circuit below, depends in part on the MOSFET. As the temperature drops, the LED illuminates, as a warning light. The 100K variable resistor has been set at a value of 55K. As the temperature drops to below 3 degrees centigrade, the LED illuminates. Altering the setting of the variable resistor, determines when the LED illuminates. When the Gate is triggered, current flows through the Drain and the Source, allowing the LED to illuminate.|
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