[sdiy] THAT300

[crystal]

hi Brian and SDIY folks,

sorry for the loooong delay, i'm dealing with medical issues serious 
enough to keep me (mostly) offline the past two months (hopefully i am 
ok now).  i AC grounded the substate which seems fine. i used a .01 cap. 
for my application perhaps i didn't need to, but for a penny or two... 
thanks for the follow up Brian.

i've also used the THAT300 in a ladder VCF with great results, so thanks 
again for the tip, Tim.

cheers,
crystal





On 5/6/2015 3:03 PM, rsdio at audiobanshee.com wrote:
> Did anyone answer this, Crystal?
>
> The substrate is typically connected to the source for 3-pin FETs, but this is BJT technology so we should disregard FET conventions.
>
> The data sheet description holds a clue: "Substrate biasing is not required for normal operation, though the substrate should be ac-grounded to optimize speed and minimize crosstalk."
>
> My interpretation of that is you should connect a capacitor to the substrate pins and ground the other end of the capacitor. No idea what value it should be.
>
> I'm surprised that there aren't example circuits in the data sheet, but perhaps there are application notes on the THAT Corp web site. The closest I could find is a mic preamplifier based on the THAT120A array, but it has a different pinout. They show pin 14 grounded, but its data sheet only mentions "grounded" not "ac-grounded," so I think they learned something before discontinuing the THAT120A.
>
> Have you made any progress since January? Keep us posted…
>
> Brian
>
>
> On Jan 2, 2015, at 3:44 PM, crystal <crystals at sonic.net> wrote:
>> Thanx Tim Ressel for the tip of using a THAT300 for a matched pair. Haven't tested my circuit out for tracking accuracy quite just yet but i bet it's a significant improvement. my question: what to do with the substrate pin?   -V, or perhaps ground?
>>
>


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