Ha, I discovered this post after replying to @devicex in the Mail Day Thread
@Dud Yep in essence I build the same thing (as I wrote here earlier:
Mail Day Thread ) You may want to have a look at the way I connected the capacitors to the LF, I used IC sockets, so that I can easily experiment with other types.
Here is an updated version of the schematic:
and here is a picture of my implementation:
As you can see in the schematic I left out the oscillator from the original schematic so my version depends on an outside source for triggering. Initially I had also not included the gating bit (the 4093 logic) to the circuit, I thought I could do this by using an external trigger, but the LF398 needs a very short pulse (a few micro seconds) which I had no source for, so I added this eventually which is why it is on a separate strip board.
So far I’ve used it with rather frequent triggers, and not noticed any drop in the output voltage between those which could affect the circuit that follows the S&H. I tried it with an oscillator frequency for a while given that the human ear is very sensitive to pitch changes and could not detect any whining / sinking of the pitch, so to speak.
Your and probably my mileage may vary with long periods between the pulses. So the IC socket approach may turn out to come in handy when the need arises to change the capacitors / experiment with other type capacitors.
Because I wanted to see when the output voltage is either positive or negative I’ve added 2 transistors that will each light an LED. Of course this is a rather course way of indicating the output voltage but it is a FUN way !
Luckily nowadays it is not so much a problem than it used to be to talk about these matters, but I just like lots and lots of flashing lights in my modules!
The attenuator potmeter drawn in the schematic near the Vout leads I ended up not adding to the module, I decided to make a separate general purpose attenuator module for that.
Best practice with CMOS chips: if you are going to build this circuit, do not forget to give the inputs of the 4093 gates that are not in use a fixed value, e.g. ground them. Otherwise the unused ports can lead to oscillations which may affect this or other circuits.