[sdiy] anti pop mosfets in minibrute

[Chris McDowell]

mmm, in this case you have a diode with the anode (fet source) at ground and cathode (fet drain) at the signal. when signal goes enough below ground, that diode becomes forward biased as the anode (ground) is 0.8ishV higher than the cathode which then conducts and clips the signal. 

anyway, simulated it, doesn't clip all that bad. good enough for arturia I guess. ¯\_(ツ)_/¯  

Chris McDowell 

> On Apr 24, 2024, at 5:24 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
> 
> Isn't the problem when the output goes *over* the forward voltage of the diodes? Below that limit , they won't conduct, or barely, anyway. In which case, keep the voltage low, but drive the current (it's a low impedance headphone output) and no problem. When the mosfets are on, the output is shorted to ground. When they're not, you're ok up to that (roughly) 2Vpp limit.
> 
> Am I just catching up on what you've already worked out? Wouldn't be the first time...;)
> 
> Tom
>  
> 
>> On 24 Apr 2024, at 21:14, Chris McDowell via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>> 
>> https://hackabrute.yusynth.net/MINIBRUTE/digital-board/schematics/MiniBrute-10-OUTPUT.pdf
>> 
>> hello list, I've been looking at minibrute schematics today and I'm puzzled by the anti pop circuitry in the headphone driver. it -seems- like the body diode of the mosfets would conduct when the signal went below 0.6ish volts (something I've run into this using mosfets for dc signal muting).
>> 
>>  From the vca page, that signal can be up to 2Vpp.  https://hackabrute.yusynth.net/MINIBRUTE/analog-board/schematics/MiniBrute-08-VCA.pdf
>> 
>> What am I missing here? Is 2Vpp just fine in this case? Now reading the 2n7002 datasheet I see the forward voltage of the source-drain diode is typ 0.88V, 1.5V max. Did I just answer my own question? 😜
>> 
>> Cheers,
>> Chris McDowell
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