I have test frequency betweest transistor vs mosfet...and the result is quite interesting

Transistor N581 = when voltage and amp increase the frequency decrease
Mosfet FDU6680 N-Channel = When voltage and amp increase the frequency will increase accordingly

kindly advise why is that so?

 

Please post your testing schematic and the testing range of frequencies and voltage/ampere.

 

Your question has no context, no information, and cannot be answered.
What test?
What frequency?
What voltage?
What current?
What circuit?
What application?

ak

 

By understanding that both transistors are completely different in there make up as well as there function, you can experiment along these lines, the 2n581 is probably a bipolar junction transistor, and your comparing it with a mosfet transistor, all bipolar transistors are current controled current sources while all mosfets are voltage controled current sources, with bipolar transistors, output impedances effect input impedances, as well as input impedances on bipolar transistors effect signal driving sources.

So first of all, experimenting needs to be done to see if the signal generator is not being effected by the transistor input circuit, of the bipolar transistor, because the generator signal itself could be given false readings ect....

You need to isolate the signal source in such a way that you can apply the same signal amplitude and frequency to both transistor circuits under test, where the signal input remains stable throughout with both transistors.

Once that is done, then you can start the process of frequency to voltage amplitude tests, with both transistors.

 

Why is the mosfet and transistor frequency the opposite?

If you'll pardon an observation - your thread title leaves much to be desired in the way of clarity and your OP offers little by way of elucidation!
HINT: Please rephrase your post with the perspective that we have no previous knowledge of your circuit!

Thanks!
HP
PS -- Please be advised that, like BJTs, MOSFETs are transistors! Hence the "T"

 

We don't know. They been actin that way for years. We've tried to get them together on this......but they won't even speak to one another.

Any suggestions?