FIELD EFFECT TRANSISTOR (FET)

Field-effect transistor (FET) is one type of transistor usingelectric field to control the conductivity of a channel of a single type of charge carriers in the material semiconducting .FET is sometimes referred to as a transistor ekakutub to distinguish a single charge carrier operations are done with two carriers operating in the bipolar transistor (BJT).

Channel

All FET having a gate line (gate), spout (drain) and source (source) which is approximately equal to the base, collector and emitter on the BJT. Besides JFET , all FET also has a fourth channel, called the body, the base or substrate. The fourth channel serves the technical purpose in pemanjaran transistorinto the operating point. The terminal is very rarely used in circuit design, but its existence is important when designing the arrangement of the integrated circuit .

The names of the FET channel refers to a function. Channel gate can be considered as controlling opening and closing of the gate really is. This gate permits electrons to flow or to prevent it by making and mengikangkan a canal between the source and the spout. Electrons flow from the source toward the spout channel if the applied voltage. Is the whole basis of the semiconductor body in which the gate, source and placed spout. Agency tract are usually connected to the highest or lowest voltage in the circuit, depending on their types. Body and drain-source channel is usually connected as a voltage source is usually connected to the highest or lowest of the circuit, but there is some use of the FET is not like this, such as circuit transmission gates andkaskoda .

How it works FET

FET to control the flow of electrons (or electron holes in the p-channel FET) from the source to the spout with a big change and the shape of a conductive channel is formed by the voltage (or lack of voltage on channel p-FET) is imposed across the channel gate and source ( to facilitate the translation, it is assumed that the body and the source is connected). This conductive channel is the channel where the electrons (or holes) flows from the source to the spout. Assuming an n-channel device mode of impoverishment . A negative voltage gate-to-source cause of impoverishment for the increased width of the area and blocking the channel from both sides, narrow conductive channel. If the impoverishment of the canal to close completely, the resistance of the channel from the source to the spout to be large, and the FET is turned off like a switch that opens. Conversely, a positive voltage to the gate-source add-channel width and allows electrons to flow easily. Now consider an n-channel device mode of enrichment . A positive gate voltage-to-source needed to create a conductive channel because it is naturally occurring in the transistor. Positive voltage attracts electrons free in the body leading to the gate, creating a conductive channel. But enough electrons to be pulled closer to the gate to fight the doping ions are added to the FET body, it forms a free area of the carrier moves is called the impoverishment, and the phenomenon is referred to as a voltage resistance of the FET.Increase in gate voltage-to-source that will further attract more electrons toward the garbang that enabled it to create a conductive channel from the source to the spout, this process is called inversion . Both the device mode of enrichment or impoverishment, if the voltage of the spout-to-source voltage is much lower than the gate-to-source, changing the gate voltage will change the channel resistance, and flow spout spout will be proportional to the voltage of the source. At this mode, the FET behaves like a variable resistor and the FET is said to operate in linear mode or ohmic mode ^[1] [2] If the voltage-to-source spout rising, it makes significant changes in channel form and taksimetrik due to the voltage gradient from the source to the spout. Form of the reversal of a thin near the tip of the spout of the canal. If the voltage-to-source spout further enhanced, thin point of the canal began to move toward the source of the spout. In this situation, said FET in saturation mode , ^[3] some people refer to it as the active mode , for the analogies with the bipolar transistor operation. ^[4] [5] Moda saturation, or the area between the linear and saturation of the strength used if desired. The area between these is often considered a part of the linear region, even though non-linear current-voltage spout spout. Even if the conductive channel is formed by the gate voltage-to-source no longer connects to the spout when the source mode of saturation, the charge carriers are not prevented from flowing. Assuming an n-channel devices, an impoverished area located on the p-type body, surrounding the conductive channel, the spout and the source area. Which includes the electron channel is free to move out of poverty if the canal through the spout is pulled by a voltage-to-source spout. Impoverishment of the area is free from the carrier and has a resistance such assilicon . Any addition of a spout on the voltage-to-source distance from the spout will add to the thin point, adding to the resistance due to the impoverishment of a voltage proportional to the voltage-to-source spout. These changes cause the current proportional-to-source spout to remain relatively remain unaffected by changes in the spout-to-voltage source and is completely different from the linear mode of operation. Thus, the saturation mode, the FET is more applicable as a constant current source rather than as a variable resistor and can be used effectively as a voltage amplifier. In this situation, the gate voltage-to-source determines the constant current passing through the canal.

The proper way to test is to use a MOSFET transistor analogmultimeter. Switch mode power supply circuits and many other uses as part of a FET transistor circuit. Leakage and MOSFET failure is quite high in the circuit and we need to know bagaimanamengetesnya. FET has a label as "Q" on the circuit board.

Measure the component that has two leads like resistors, capacitors and diodes is much easier than measuring and FET transistor which has three legs.

I. First, find the door gate , drain and source pins. From the book or search for a replacement semiconductor datasheet from search engines.

II. Once you have a cross reference or pin diagram for each MOSFET, then use an analog multimeter, set to a size of 10K ohm.Assuming the n channel MOSFET test probe then put the black on the pin DRAIN .

III. Touch the GATE pin to probe the red to clear the internal load capacitance of the MOSFET. Now move the probe red probe to SOURCE pin while black is still touching the DRAIN pin. Use your right index finger and touch and DRAIN GATE simultaneously. Would seem multimeter needle will move forward into the middle of the meter scale.

IV. Lift the probe is red from the SOURCE pin and put it back again to the SOURCE pin; pointer will still be in the middle of the meter scale. To empty, probe the red should be lifted and touched one padapin GATE. This in turn will release the internal capacitance again.

V. At this time, use the probe red pin touch SOURCE again, the pointer will not move at all because we had emptied the charge by touching a pin GATE . This is an example MOSFET is in good condition.

VI. If it is seen that all the measured results pointer (needle) moves toward zero ohms and will not let go, then the FET is considered shorted and needs replacement.

Testing of P-channel FET transistor effect fieldsame way as when examining the N-channel FET. Thing to do is to reverse the polarity of the probe when examining the channel P. Make sure you use a meter that has a range of 10k ohms.

Example : N-channel FET 2SK791, K1118, IRF634, IRF 740 and P-channel FET J307, J516, IRF, 9620 and others.