BS170 switch from drain to source without pop

[acehobojoe]

Is this possible at all? I was building a buffer based on a few projects i'm familiar with, and for the life of me, I can't switch it to the source without a pop! there must be some way for "slow" switching, or something.

I've tried a few different things, like adding PDR's on all outputs, yet, nothing has worked. any suggestions are appreciated!

Here's my schem!

[thelonious]

Move C3 to between BS170 source and the switch. Use poly film cap for C3 instead of electrolytic. After that, place a 2.2M resistor across the switch terminals if necessary.

There is DC on your source - moving C3 prevents it from reaching the switch and causing pop. You don't need C3 where it currently is because you already have C2 as an output cap for the drain.

[acehobojoe]

I have updated the schem :



However, don't know if that's what you meant by the 2.2m . . maybe you meant literally across the terminals connecting them?

anyways, about to test it.

[samhay]

Get rid of C3 and R5 - neither are doing anything useful, and C3 can cause problems.
If it still pops, try making R6 smaller - 100k would be a good choice. If you still have problems, add a large - 1M+ resistor between lugs 1 & 3 of the switch.

[acehobojoe]

ok great!
here is the final schem.

[thelonious]

That last schem looks good. Did the pop decrease? What samhay said re the 1M+ resistor across lugs 1&3 of switch is what I meant w/ the 2.2M.

[acehobojoe]

ok great. actually, I already boxed it up and it has been one of the most useful circuits so far that I've built.

and it worked perfectly on the first try!