Pin identification method for junction field-effect transistor

Pin identification of junction field-effect transistor:

Determine gate G: Set the multimeter to the R × 1k position, connect any negative electrode of the multimeter to one electrode, and sequentially touch the other two electrodes with the other probe to measure their resistance. If the resistance values measured twice are approximately equal, then the negative probe is in contact with the gate, and the other two electrodes are the drain and source Swap the drain and source, and if the resistance measured twice is high, it is an N-channel; If the resistance values measured twice are both very small, it is a P-channel.

Determine the source S and drain D:

There is a PN junction between the source and drain, so the S and D poles can be identified based on the difference in forward and reverse resistance of the PN junction Measure the resistance twice using the exchange probe method, with the lower resistance value (usually several thousand ohms to tens of thousands of ohms) being the forward resistance. At this time, the black probe is connected to the S pole and the red probe is connected to the D pole.

Comparison between field-effect transistor and transistor:

Field effect transistor is a voltage control element, while transistor is a current control element Field effect transistors should be used when only a small amount of current is allowed to be drawn from the signal source; When the signal voltage is low and more current is allowed to be drawn from the signal source, transistors should be selected.

The working principle of a transistor is completely different from that of a field-effect transistor, but each pole can be approximately matched for ease of understanding and design:

Transistor: Base emitter collector

Field effect transistor: gate source drain

It should be noted that the emitter potential of the transistor (NPN type) is designed to be lower than the base potential (about 0.6V), and the source potential of the field-effect transistor is higher than the gate potential (about 0.4V).

Field effect transistor (FET) is a unipolar device that uses majority carriers to conduct electricity, while transistor is a bipolar device that uses both majority and minority carriers to conduct electricity.

Some field-effect transistors have interchangeable source and drain electrodes, and their gate voltages can be positive or negative, making them more flexible than transistors.

Field effect transistors can operate under very low current and voltage conditions, and their manufacturing process can easily integrate many field effect transistors on a single silicon wafer. Therefore, field effect transistors have been widely used in large-scale integrated circuits.