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Diode in Amplifier

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Hi Perhaps even more interesting to know that these mosfet no Oficial Hitachi but a Chinese with no mark.
Attached a sketch as I have measured the fet.
 

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  • 2SK213 Drawing.pdf
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Hi,

Yeah sorry but that's no good. You need a resistor between the pot and the gate too, like 10k.
Then measure the voltage gate to source and do a plot.
 
hi,
The potentiometer is 10k and is connected to the supply voltage with a side, the other side is connected to ground and the runner is located on the gate of the FET,
 
Your sketch does not shows the supply voltage of your test. Maybe it is higher than the absolute maximum allowed voltage of 15V listed on the datasheet. you said 16V before.
If there is a 9.1V zener diode from the gate to the source then it will be instantly burned out if the pot is turned up to maximum unless you add a resistor in series with the gate pin.
 
Hi,
The power supply I have varied between 10 and 32 volts there then walked about 80 ma on the 100 ohm resistor in the drain pipe.
I then the 10k potentiometer in the greatest value was to the supply voltage slowly twists with a digital multimeter between gate and source voltage that I have run up to about 16 volts.
And the multimeter reversed to see if there was a zener diode to measure.
There was to be measured with the meter in two different directions is no differenceand.
And the fet remained intact.
 
Hi,

Well if you dont do as we suggest then you're on your own.
 
Hi,

I'm going to try it out with a resistor in the direction of Gate 10K.
And with two voltage meters, one between Gate and Source, and an over voltage + and -.
 
Hello,

That sounds good. You may have to try this on a new device now though because the previous device you already tested may have had the zener destroyed already. It may be ok, but it could be blown open so it would be best to start with a new device that has never been used yet.

A question does come up though, do we know what the zener voltage is supposed to be for these devices?
 
Hi, new 2SK213, supply 20 volts Drain connection on the outside potentiometer.
Potentiometer other side to the mass.
Gate / Source voltage 15 volts over 10K resistance state than 0,295 volts, test probes on Gate and Source two sides I measured, Discover no presence of a zener.
 
Hi,

What is the 0.295 volts for, where did you read that?
 
Hi,

Yes i think we understood the hookup, but what is that 0.295 volts ?
BTW you can upload gifs and jpgs, you dont have to make pdf's all the time.
 
Hello again,

Ok that is much better :)
What voltage do we expect to see it zener at anyway? Is it 15v or lower?
 
Hi, I read in an article about the zener in mosfets that it is 10 volt zeners.
In the amplifier design are 9V1 zener, so the only conclusion is that in these chinese Mosfets no zeners down, that does not surprise me.
I have fets from China received the 2SJ109 and 2SK389, and that were to be both NPN transistors.
I get original Hitachi mosfets soon.
I will again measure.
 
Hi,

Ok, and also, what are you using to make these measurements, is it a digital meter and do you know the input resistance of it on the DC scale?
 
Hi, I have another mosfet 2SK3497 tested, even there a zener diode in it.
I went up voltage of 14 volts Until Gate / Source.

12 volts is recommended, No zener diode.
 
Why are you playing with Japanese parts when we cannot believe their datasheets? This one is from Toshiba and the other one was from Hitachi.
 
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