ratela.blogg.se - Transistor as a switch download

All forms are available in both N-channel and P-channel versions.

Insulated-gate devices can also be sub-divided into Enhancement types and Depletion types.

Field Effect Transistors, or FET’s are “ Voltage Operated Devices” and can be divided into two main types: Junction-gate devices called JFET’s and Insulated-gate devices called IGFET´s or more commonly known as MOSFETs.

Transistor Tutorial – The Field Effect Transistor

The NPN transistor requires the Base to be more positive than the Emitter while the PNP type requires that the Emitter is more positive than the Base.

This helps prevent any induced back emf’s generated when the load is switched “OFF” from damaging the transistor.

Inductive loads such as DC motors, relays and solenoids require a reverse biased “Flywheel” diode placed across the load.

A transistor can also be used as an electronic switch between its saturation and cut-off regions to control devices such as lamps, motors and solenoids etc.The Collector or output characteristics curves can be used to find either Ib, Ic or β to which a load line can be constructed to determine a suitable operating point, Q with variations in base current determining the operating range.The standard equation for currents flowing in a transistor is given as: I E = I B + I C.The Base-Emitter junction is always forward biased whereas the Collector-Base junction is always reverse biased.Requires a Biasing voltage for AC amplifier operation.The most common transistor connection is the Common Emitter (CE) configuration but Common Base (CB) and Common Collector (CC) are also available.The arrow in a transistor symbol represents conventional current flow.Bipolar junction transistors are “ Current Operated Devices” where a much smaller Base current causes a larger Emitter to Collector current, which themselves are nearly equal, to flow.There are two main types of bipolar junction transistors, (BJT) the NPN and the PNP transistor.The Bipolar Junction Transistor (BJT) is a three layer device constructed form two semiconductor diode junctions joined together, one forward biased and one reverse biased.

Having looked at the construction and operation of NPN and PNP bipolar junctions transistors (BJT’s) as well as field effect transistors (FET’s), both junction and insulated gate, we can summarise the main points of these transistor tutorial as outlined below: