場效應管(mos管)如何判斷好壞（How can a field effect tube (MOS tube) be judged good or bad）

1、場效應管(mos管)如何判斷好壞（How can a field effect tube (MOS tube) be judged good or bad）(I) detection of junction type field effect transistors1. distinguishing electrode and tube typeWith a multimeter R * 100 * R file or 1K file, with the black pen connected with an electrode, with the red pen in order to to

2、uch the other two electrodes. If the measured one electrode and another two electrode resistance were large (infinite) or resistance are small (a few hundred ohms to one thousand ohms), you can determine the black pen then is gate G, the other two electrodes, respectively is the source and drain D S

3、.In the primary measurement of two resistances with high resistance, the tested tube is P channel junction type field effect transistor. In the primary measurement of two resistances with low resistance, the tested tube is N channel junction type field effect transistor. The positive and reverse res

4、istances between any two electrodes of a junction type field-effect transistor may also be measured arbitrarily. If the positive and negative resistances between the two electrodes are equal to several thousand ohms, the two electrodes are drain D and source S, and the other electrode is gate G.The

5、source and drain structures of junction type field effect transistors are symmetrical in structure and can be used interchangeably. If the positive and reverse resistances of a field effect transistor are measured to be 0 or infinity, the tube is broken or has been opened.2. testing its magnificatio

6、nWith a multimeter R * 100 files, the red pen is connected with the field effect transistor source S, the black probe connected to the drain electrode D, measure the resistance value between the source and drain after RSD, and then hand the letter gate G, the multimeter pointer will swing to the lef

7、t or right (the majority of FET RSD the left hand is increased, less number of swing; RSD FET will decrease, swinging to the right hand). As long as the hand has a substantial swing, that the measured tube has a larger amplification capability.(two) detection of double gate field effect transistorsD

8、iscrimination of 1. electrodesMost double gate pin position sequence of field effect transistor is the same, namely from the field effect transistor (back at the bottom of the tube), followed by anti clockwise to drain source D, S, G1 and G2 gate gate. Therefore, as long as the drain D and the sourc

9、e S are measured by a multimeter, two gates can be found.When testing, can be placed on R * 100 multimeter, with two probes were measured for positive and negative resistance between any two pin values. When the measured reverse resistance between the feet are a few tens of ohms to several thousand

10、ohms (the rest of the resistance between pin values are infinite), the two electrode is the drain and source of D S, the other two electrodes for G1 gate and gate G2.2. estimating magnificationWith a multimeter R * 100 files, the red pen is connected with the source S, the black probe connected to t

11、he drain of D, while RSD value in measuring resistance and the source drain D S between the two gate pinch with your fingers, with the human body induction signal. If the induction signal is added, the resistance value of RSD is changed from big to small, which indicates that the tube has certain am

12、plification capability. The larger the pointer to the right, the greater the magnifying power.3. judge whether it is good or badThe resistance values between field effect transistors, source S, and drain D are measured in meters R * 10 or R * 100 files. Normally, the positive and negative resistance

13、s are tens of ohms to several thousand ohms. The resistance and the black probe connected to the drain of D, the red pen is connected with the source S when the measured value of the resistance of the black probe connected to the source S, the red pen then D when the measured value is slightly large

14、r. If the resistance between the D and the S poles is 0 or infinity, the tube is broken or damaged. Use multimeter R * 10K file to measure the resistance value of the other pins (except D and S). Normally, the resistance values between the gate G1 and G2, G1 and D, G1 and S, G2 and D, and between G2

15、 and S should be infinite. If the resistance is not normal, the performance of the pipe is poor or damaged.(three) detection of VMOS high power field effect transistors1. determine the electrode and tube typeThe positive and reverse resistance values of any two pin of the field effect transistor are

16、 measured with a multimeter * R * 100. In one measurement, the resistance of the two pin is several hundred ohms,When the two pen connected pin for S source and drain D, while the other pin gate G.Measure the positive and negative resistance values between the two pins (drain D and source S) with th

17、e multimeter * R * 10K. When normal, the forward resistance is about 2K, and the reverse resistance is greater than 500K.In the measurement of reverse resistance value, the red pen pin does not move, the black pen from the pin, and the first gate G touch, and then to pick up the original pin, observ

18、e the change of multimeter reading. If the multimeter reading from the original large turns 0, the red pen is received by the source S, the black pen are connected to the drain D. The gate G is indicated by the black meter stroke, indicating that the tube is a N channel fet. If the multimeter readin

19、g is still larger, while the black pen back to the original pin unchanged, to the red pen to touch the gate after the G back to the original pin, if the multimeter reading from the original high resistance to 0, then the black probe connected for source S, the red pen is connected to the drain D. Th

20、e red pen trigger grid G is valid, indicating that the tube is a P channel fet.2. judge its good or badMeasure the positive and negative resistance between the two feet of a field effect tube by using a multimeter R * 1K or R * 10K. Normally, the positive and reverse resistances between the remainin

21、g pins (G and D, G and S) should be infinite when the forward resistance value of the drain and the source is smaller. If the resistance between two poles is close to 0, the damage of the tube has been found out.In addition, can also be used to trigger the gate (trigger, P channel field-effect trans

22、istor with the red pen N channel field-effect tube black probe trigger) method to determine the field of pipe is damaged. If the trigger is effective (the positive and reverse resistances of the D and S poles are changed to 0 when the gate G is activated), the performance of the tube is determined.3

23、. estimate its magnificationN channel VMOS field effect transistor, multimeter (R * 1K) black probe connected to the source S, the red pen is connected with the drain gate at D, G open circuit; multimeter indication of resistance is higher. Then contact the gate G with the finger to add the human in

24、duced signal to the pole. If the induction signal is added and the pointer of the multimeter is deflected greatly, it shows that the tube has a stronger magnification. If the hands do not move or deflect slightly, the tube amplification ability or amplification ability.It should be noted that this detection method is not applicable to a few VMOS high power field effect transistor