Most likely the extra letters and numbers "Y64K DK" are there to indicate features or packaging options, the factory, and/or the date of manufacturer.

You can measure the input capacitance if you do so in accordance with the conditions specified on the datasheet.

For example on the Vishay datasheet (www.vishay.com/docs/91070/91070.pdf) the conditions given are:

VGS = 0 V,
VDS = 25 V,
f = 1.0 MHz, see fig. 5

Hola Dick

When they measure to produce the above data, what instruments do they use?

 

I tested them with cheap DMM (diode test) which is powered by 9V battery.

How comes, Willen? Diode test is made measuring voltage drop, usually with a constant current around 1 mA provided by the multimeter. How can you get capacitance?

Weren't you go to use the capacitance meter in your DMM?

 

How comes, Willen? Diode test is made measuring voltage drop, usually with a constant current around 1 mA provided by the multimeter. How can you get capacitance?

Weren't you go to use the capacitance meter in your DMM?

Hola atferrari,
You understood wrongly, I mean I tested MOSFETs with diode test/continuity test mode of DMM to know the condition (damaged or fine) same as BJT testing. And I measured gate capacitance of the FET with Capacitance mode of DMM.

 

Hola atferrari,
You understood wrongly, I mean I tested MOSFETs with diode test/continuity test mode of DMM to know the condition (damaged or fine) same as BJT testing. And I measured gate capacitance of the FET with Capacitance mode of DMM.

Good. Now I understand. Sorry for the confusion.

 

The result about gate capacitance of my unknown IRF840 made me frustrate!

IRF830 genuine fast FET= 700pf
IRFz44 slow FET= 1.8nF
IRF840 unknown FET= 1.7nF
7N60 power FET= 1.5nF

the IRF840 seems counterfeit part! What the h___! IRF830 and IRF840 should have almost similar gate capacitance, should't it?

I did forsee this result in post #2. I would not conclude you had a counterfeit part on the basis of one measurement. If you were to construct a test circuit in which you could exchange the good part for the suspect part and demonstrate different behavior that would be a great deal more convincing.

 

If you have an o-scope, feed the mosfet a 100k Hz square wave signal through a 100, 1k, 10k and 100k resistor. You should see the square signal decay to a shark fin. Compare the resistance where the shark fin forms. Alternatively, you can do it with increasing frequency at a constant gate resistance.,


Easily measured.

 

Hola Dick

When they measure to produce the above data, what instruments do they use?

I do not know.