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  1. AFex54

    SOT-23 Transistor ''750'' marking?

    I looked thoroughly and couldnt find what part this is. there was only a couple SOT23 part codes online that even contained ''750'' and they are diodes. There are a large number of them located in the power supply input area of a graphics card for a computer.
  2. AFex54

    How to make this circuit unity gain?

    https://i.imgur.com/2g5Hoeg.png I built this amp but the gain is unncessary I just need it to be a buffer between the headphones and source to supply the power the headphones need. I think the way to achieve this is to remove the caps and resistors on the op amp's inverting inputs but will this...
  3. AFex54

    Volume control potentiometer is mute for first 10%?

    I built a simple volume control using a 47k log pot and it works great except for the first the 10% of where it is mute and then jumps up in volume, the remaining 90% is good and precise ... is this because the resistance too high? If the resistance is a too high and I were to add a resistor...
  4. AFex54

    4066 switches leaking in sample and hold circuit?

    Hi, I'm having a problem when using a 4066 switch in my sample and hold circuit, when I used a mechanical SPST switch to test the S&H circuit when it was on the breadboard it worked great so I know there's nothing wrong with the circuit itself. when I use the 4066 switch it seems to be leaking...
  5. 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...
  6. 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...
  7. 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...
  8. 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?
  9. 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...
  10. 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...
  11. AFex54

    dual opamp, only need 1?

    the circuit only needs one op amp, I have lots of TL082s and im wondering what I should do with the unused op amp? leave it be? or something else? thanks
  12. AFex54

    frequency range too small on 555 timer circuit?

    http://www.electroschematics.com/5834/pulse-generator-with-555/ I breadboarded this 555 pulse generator and the duty cycle adjustment is very good however i cant get the frequency range I would like, it is very limited to the point of only noticing a change in frequency at either extreme of the...
  13. AFex54

    will a basic buffer be sufficient?

    So I need to buffer the gate and CV signals from my CV keyboard, what kind of circuit would you recommend? its a fairly lofi device but i still want to make it work as best as possible, I suspect the diagram below is the ideal buffer? would it need a few more components to tailor it for my...
  14. AFex54

    sample and hold pulse source?

    I would like to be able to sample and hold white noise for random voltages but I need a very short pulse for this. I need a 50µs or less pulse with a general frequency range from about 50ms to 3 seconds, Unless a 555 can operate at these extreme Im not sure how else to achieve this, help is...
  15. AFex54

    Does clock pulsewidth affect the 4017 ?

    edit: think I figured it out , the gate is a constant signal that is switched between steps with each pulse, so to answer my own question the length of the pulse has no effect.
  16. AFex54

    When should you buffer a signal?

    I dont know where or when my signals need current buffering, I feel buffering randomly could cause a circuit to malfunction, but I do know I need it. Is someone more knowledgeable could shed some light on this that would be great!
  17. AFex54

    Converting Hi pass to Lo pass

    I would like to make high pass clone of this simple low pass filter, After a bit of research I think I need to invert the filter and feedback components to do this, C9 and C10 become R35s and R35 becomes C9/C10? Heres some info and the schematic (VCF in bottom left) : It is a low pass "T" type...
  18. AFex54

    Ideas for simple pulse circuit?

    Need some ideas for generating a repeating slow pulse from 0v- 9v lasting around 250ms with pulsewidth adjustment. A square LFO of sorts. any help/input would be appreciated as im fairly new
  19. AFex54

    would it be possible to run this circuit with a single 9V supply?

    http://www.musicfromouterspace.com/analogsynth_new/SAWTOTRICONVERT/SAWTOTRICONVERT.php really need a ramp to triangle converter for integrating into the MFOS Noise toaster. I would of course prefer to stick with MFOS designs for assurance that it is 'musical grade'. So any Ideas if it would be...
  20. AFex54

    Modifying this oscillator to achieve lower frequencies?

    http://www.instructables.com/id/THE-SIMPLEST-FUNCTION-GENERATOR-BUILT-ON-A-BREADBO/ I was drawn to this oscillator because it uses an LM324 which i happened to have lying around and it also has 3 waveforms, including a sine which i needed. however its frequency range is not ideal, it goes well...
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