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  1. AFex54

    A means of closing a JFET switch with a postive voltage?

    im not sure if you understand what I mean when I say I just need a hold circuit. In the typical S&H a JFET could allow independant control of sampling, so an AC input could be sampled at any point from peak to peak, I dont need this, I just need to maintain the DC input from the keyboard once...
  2. AFex54

    A means of closing a JFET switch with a postive voltage?

    ok yeah that makes sense
  3. AFex54

    A means of closing a JFET switch with a postive voltage?

    ? in place of the DG403 would be the mechanical switch, there is no DG403. the only thing about that circuit that Is important is the fact that there is no voltage follower before the switch like in most other sample and hold circuits, the signal from my keyboard could go straight into the...
  4. AFex54

    A means of closing a JFET switch with a postive voltage?

    now im also confused, preventing the sampling cap voltage from decaying? isnt that what 'holding' a sample is? and the diode preventing the flow to ground, firstly i dont see the path to ground in any S&H circuit from the diode, and I dont see how an open switch wouldnt prevent the flow aswell...
  5. AFex54

    A means of closing a JFET switch with a postive voltage?

    they pass my control voltage? I was implying the DG403 was simply a mechanical switch (a keyboard key)
  6. AFex54

    A means of closing a JFET switch with a postive voltage?

    I was looking for one of those sample and hold chips in the beginning but I couldnt find any available. but I think now even my diode idea would be unnecessary (it would cause a voltage drop anyway right?), in this even simpler circuit the switch could be my keyboard key, the typical first...
  7. AFex54

    will this really give me a triangular wave?

    unfortunately yes thanks that was really helpful
  8. AFex54

    Simple way for LED to indicate at 2 different brightness's

    the 4017 is just and extension of the circuit, it wouldnt disturb the circuit above. really what im wondering is what happens when the lower current signal and higher current signal from the 555 combine/meet ? my thought was maybe I needed to use a JFET to pinch closed the low current signal...
  9. AFex54

    A means of closing a JFET switch with a postive voltage?

    my thought was that instead of adding an electronic switch I could take advantage of the mechanical switch in the circuit. original plan : as you can see the only time the JFET would be closed is during a sample (but thats only if the JFET could be closed with positive voltage WHICH IT CANT...
  10. AFex54

    will this really give me a triangular wave?

    any idea how significant the decrease would be? my synth is LoFi to begin with so if its only slight then I doubt it would pose too much of an issue.
  11. AFex54

    will this really give me a triangular wave?

    I realise there will be distortion but Im talking about an isoceles triangle , my synth already has a ramped wave (which is techincally also triangular) so if this converter is too ramped I dont see the point in using it. for example this amount of distortion would be more than perfect: I...
  12. AFex54

    A means of closing a JFET switch with a postive voltage?

    Hmm I was thinking about this and Im wondering do I actually need a switch in my circuit? I will post in earlier thread of mine in regard to the sample and hold circuit so because the only time there is an input into the sample and hold circuit is during a sample the only function of the JFET...
  13. AFex54

    will this really give me a triangular wave?

    its essentially just a low pass filter, so I feel like im always going to end up a with more of a curvy ramped wave on the output. Is this the case? perhaps I need to find the triangular sweet spot by adjusting the value of C2 and R5? Also the device that produces the square wave also has a...
  14. AFex54

    A means of closing a JFET switch with a postive voltage?

    I need to close the JFET in my sample and hold circuit with a postive voltage, the reason being the sampling must be triggered by a keypress of my CV keyboard, so this mean using the 9V gate signal from the keyboard. I made a schematic of an idea for this but im fairly sure it wont work, however...
  15. AFex54

    Simple way for LED to indicate at 2 different brightness's

    ok , so other than that it should behave as I described ?
  16. AFex54

    Simple way for LED to indicate at 2 different brightness's

    Im building a simple 10 step analog sequencer with a 4017 decade counter below is an extracted circuit of a step indicating LED for a single step of the sequencer, I need to indicate 3 things with the LED off -step inactive on, dim -step active, gate off on, bright - step active, gate on what i...
  17. AFex54

    biasing this op amp

    and i suppose having a stock up components will motivate me to build more stuff too :)
  18. AFex54

    biasing this op amp

    sure haha but I just hope the post doesnt start with: 'this will be my 5th time ordering op amps...'
  19. AFex54

    biasing this op amp

    yeah sorry, my issue is that I pay far too much attention to the specs on RS instead of checking the actual data sheets. thanks for the help, and I hope this is the last time I post about this in this thread :)
  20. AFex54

    biasing this op amp

    this will be my fourth attempt at getting the right op amp, :( I now have TLC2264s, 2274s and LM324s, 0-8V with the 324 would have been fine but there was another problem ...input bias current. now I can get the TS942 is on Mouser but shipping is €20. tthe only remotely suitable one on RS is...
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