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Electronics => Beginners => Topic started by: eev_carl on May 16, 2018, 06:50:01 pm

Title: Max Vgs on J211 Datasheet
Post by: eev_carl on May 16, 2018, 06:50:01 pm

Hi,

I was wondering what the Max VGs(off) = -4.5V value in the J211 datasheet is.  I'm getting 0uA when I go to the Min VGs(off) cutoff of -2.5V and didn't see any change when I moved VGs lower (more negative).  I have a 220 ohm resistor at the drain of a test VCR circuit.

Datasheet: https://www.mouser.com/datasheet/2/308/J211-1120841.pdf (https://www.mouser.com/datasheet/2/308/J211-1120841.pdf)

Thanks,
Carl

Title: Re: Max Vgs on J211 Datasheet
Post by: fourtytwo42 on May 16, 2018, 07:30:25 pm

Its the range of cutoff voltage across a selection of devices, you will never need more than -4.5V to get cutoff but some will cutoff as low as -2.5V :)

Title: Re: Max Vgs on J211 Datasheet
Post by: eev_carl on May 16, 2018, 08:54:57 pm

Does that mean that there are some J211's out there that won't cutoff at -2.5V (all 3 that I tried cut off at -2.5V)?  Is the difference in packaging?  The datasheet has an MMBF packaging for a surface mounted device that I didn't try.

Title: Re: Max Vgs on J211 Datasheet
Post by: fourtytwo42 on May 17, 2018, 07:27:50 am

I think it just to allow them latitude for process variations so you should design your circuit to be abe to operate across the full range unless you want to follow a select on test procedure (can be expensive).
As you can see they do not state a typical!

Title: Re: Max Vgs on J211 Datasheet
Post by: Kleinstein on May 17, 2018, 01:51:40 pm

The cut off voltage with JFETs shows quite a lot of scattering between units. When you buy a few from the same batch, chances are they are a little closer together, but next batch can be quite different.

The difference is not from the package, but from making the silicon chip.