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I have a sine to pulse converter box(LM2903 is used), it works very well and I also have the circuit schematics. The converter converts the mV level sinusoidal signals to pulses.

I want to rebuild it so first I drew it in LTSPICE but it doesn't work. It outputs constant negative voltage not pulse for given sinusoidal input signals.

What is wrong?

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  • \$\begingroup\$ Looks like 20 Hz @ 0.1 v? How long are you simulating? \$\endgroup\$ – johnnymopo Nov 28 '15 at 1:15
  • \$\begingroup\$ I tried 0.01V as well I simulate 1 sec or 10 sec both wont work. I get negative voltage. \$\endgroup\$ – user16307 Nov 28 '15 at 1:17
  • \$\begingroup\$ ok it simulated in another software. check out: electronics.stackexchange.com/questions/203130/… \$\endgroup\$ – user16307 Nov 28 '15 at 2:41
  • \$\begingroup\$ Interesting did you try the LTSPICE version without the 220 ohm load? \$\endgroup\$ – johnnymopo Nov 28 '15 at 2:43
  • \$\begingroup\$ yes I tried it gives huge constant voltage n that case. \$\endgroup\$ – user16307 Nov 28 '15 at 2:44
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Oh, I know why it's not working without even trying it. The 2903 has an open-collector output and you've tied the load to ground. It's possible you have some other error besides this though.

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  • \$\begingroup\$ what can I do to fix it? \$\endgroup\$ – user16307 Nov 28 '15 at 15:41
  • \$\begingroup\$ Tie the load (R6) between output and the supply V1 instead. See this similar (in that respect) question: electronics.stackexchange.com/questions/201511/… \$\endgroup\$ – Fizz Nov 28 '15 at 15:42
  • \$\begingroup\$ it still doesnt work i get constant output \$\endgroup\$ – user16307 Nov 28 '15 at 15:45
  • \$\begingroup\$ @user16307: Then upload the asc file to pastebin. I don't feel like redrawing all of it. \$\endgroup\$ – Fizz Nov 28 '15 at 15:45
  • \$\begingroup\$ which file? file for the comparator? \$\endgroup\$ – user16307 Nov 28 '15 at 15:47

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