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  1. AFex54

    why is my op amp doing this?

    Im using an lm324 and a 9V supply with this circuit. the output will sit around 8V and will not hold a sample it justs climb back to this voltage after opening the switch, I tried this with a tl074 and it behaves correctly , what is the issue with using an lm324?
  2. AFex54

    frequency range too small on 555 timer circuit?

    sounds great and looks surprisingly simple! I'll have to do some reading on inverters first to know whats actually going on
  3. AFex54

    biasing this op amp

    I was actually reading the datasheet of the TLC2274 initally but of course ended up buying the 2264, talk about careless. well at least I can buy the 2274 in singles
  4. AFex54

    biasing this op amp

    noooo, so much money wasted on these rail to rails too! and +/- 4.5V would only work from an actual split supply?
  5. AFex54

    biasing this op amp

  6. AFex54

    biasing this op amp

    right give me a few mins to draw it up
  7. AFex54

    biasing this op amp

    woops ha, another lesson learned for again :) Im such a noob...
  8. AFex54

    biasing this op amp

    my last reply was full of misinformation, but sorry for the long delay, I was in germany on holidays. having weird issue . my rail to rail op amp, regardless of the voltage range ,e.g 0-6V, I apply from the potentiometer voltage divider to the non-inverting input (in the first stage of the...
  9. AFex54

    biasing this op amp

    the sampled voltage is taken from pin1 of R2 though, does this make a difference? I have no idea what DC coupling is so sorry if it makes no difference to what you just said
  10. AFex54

    biasing this op amp

    There actually isnt a problem after all, R2, the resistor on R1s output, reduces the voltage range to 0-7.5V anyway, so all I need to do is sample the voltage after this resistor.
  11. AFex54

    biasing this op amp

    ok, I sent Ray an email It was a lot of info for one email but I think hes familar enough with the designs to understand it Also 0-8 would be a sufficient range aslong as it 1-9V, the reason being is the noise toaster oscilator is capacble of very low frequencies and it becomes inaudable at...
  12. AFex54

    biasing this op amp

    yes prices really are terrible but the delivery is extremely fast and very cheap. unfortunately the circuit I drew doesnt have any room for change other than the sample and hold itself. its gets rather complicated if I try to explain it but here goes 9V is the supply of the synthesizer ive...
  13. AFex54

    Reason for using JFET transistors in sample and hold?

    perfect answer, thanks :)
  14. AFex54

    Reason for using JFET transistors in sample and hold?

    I notice even the most basic sample and hold circuits use a JFET transistor rather than simply using a bipolar npn. all the transistor has to do is act as an on off switch to allow a sample of the input voltage through, JFET are voltage controlled , I cant see the point of using one if all you...
  15. AFex54

    biasing this op amp

    http://ie.rs-online.com/web/p/operational-amplifiers/6611577/ this is what i could find on RS, seems to be fit for the purpose, operates with 9V single supply ,rail to rail, but just want to make sure im not overlooking anything since their hardly cheap
  16. AFex54

    biasing this op amp

    I meant if it was out of the question with a single supply, the components dont matter as long it does what i need. thanks, the OPA4342 seems like it would work. the only catch with rail-to-rails is the bigger price tag then?
  17. AFex54

    biasing this op amp

    the trouble is I need to be able to sample the full 9V, is this out of the question? would there be a suitable rail to rail ,single supply chip I could get?
  18. AFex54

    biasing this op amp

    sorry, I meant to say I have a single supply, I created a virtual ground with a 4.7k resistor divider, but im strugglin to communicate it with the circuit, i tried connecting to the noninverting input but it doesnt work Also I am using a TL082 , would I need to get a rail to rail op amp?
  19. AFex54

    biasing this op amp

    I know, that what the part i need help with! im using a split supply and tried connecting the virtual ground in many different ways but ever time the circuit stops working when i do oh ok didnt realise you could upload here I made it
  20. AFex54

    biasing this op amp

    I was hoping i could finally move on to the final wiring of my project but i realised I had forgotten a vital piece. I needed a very simple sample and hold circuit and this is my design so far: It sample perfectly but Im struggling to get the op amps working the way they should, they are 1.5V...
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