Re: Hempt?


Gordon REASON <gordonj.reason@...>
 

Ben , a good test to find the Iss of a fet ,

Very sensitve devices , I sometimes felt , that even blowing over them , would creat enough static to damage them

But , for an FG35 hempt , out of any circuitry ...........

Link the gate to the source .

Connect carefully , with short Wires , to a low voltage variable power supply , a 3 Volt battery is ideal with an adjustable output voltage  ( an LM317 )  and multiturm pot , and a mA meter in the output + line .

Set the output to Zero .

Connecy Positive to the Drain , and Negative ( common) to the emitter .

Slowly increase the Positive supply ........ at some 600 mV , the mA should be indicating around 50 to 90 mA

and at One volt , DO'NT GO HIGHER ,     the current should stablise at 80 to 110 mA

You have a good idea of your Idss ......

Turn the voltage back down to Zero , before removing wires .

For low noise Fets  60 to 80 mA

For medium power amps , 80 to 150 mA

Used to do this on a little jig , to select Fets used in a multstage amplifier ...... it worked very well and made alignment a breeze ..............




On 26 March 2021 at 14:05 "militaryoperator via groups.io" <Military1944@...> wrote:


I love it when you win a little. 

Thought I'd see how much current LNA was pulling. It said 5ma. Thought a bit low as destructions say twiddle pot for 10ma drain I.

Opened up little box and with 2 pairs of specs on saw wire off. Resoldered wire, 20ma. 

Just put it on specy with sig gen running at 1/4f and bingo, amplification at 10Ghz. 

I like it when a plan comes together.

Many thanks for the advice, pointers and offers. 

Ben G4BXD 

 

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