enter image description here

I made the circuit above by using LTSpice where I can amplify weak, badshaped pulselike signals, shift their levels, and convert them to positive pulses. At the end I obtain a pulse train with adjustable offset and amplitude. U1 U2 U3 are universal amplifiers in LTSPice. But I am planning to use LM324 opamp for these. Here is the circuit:

Click here to see it bigger: https://i.stack.imgur.com/H0I5L.png

![enter image description here][2]

My question is this circuit looks ok at Spice program but I didnt implement it.

Any idead about resistor, poti values? Do I need capacitors or diodes? Since I'm not a professional designer, I would like to have your opinions before actually solder/implement.

  • \$\begingroup\$ Don't you think it would be interesting to know what components U1,U2 and U4 are (did I just overlook U3?)? \$\endgroup\$
    – PlasmaHH
    Mar 31, 2015 at 9:20
  • \$\begingroup\$ Thanks I just edited. U1 U2 U3 are called universal amplifier in LTSpice so would be also good to have suggestions on that. the last part acts as Schmitt Trigger. I plan to use LM324 but have actually no idea if it is ok.. \$\endgroup\$
    – user16307
    Mar 31, 2015 at 9:24
  • \$\begingroup\$ Why didn't you simulate with LM324 op-amps? Also, the circuit is very tiny and difficult to read. \$\endgroup\$
    – Andy aka
    Mar 31, 2015 at 9:44
  • \$\begingroup\$ Remove added diagram if not wanted. \$\endgroup\$
    – Russell McMahon
    Mar 31, 2015 at 10:02
  • \$\begingroup\$ @Andy aka i checked there is no LM324 in LTSpice. Click here to see it bigger:i.stack.imgur.com/z0Ngl.jpg \$\endgroup\$
    – user16307
    Mar 31, 2015 at 10:19

1 Answer 1


You can import the LM324 into LTSpice following this link. Below is the section you need to read and follow: -

enter image description here

This will give you the simulation results that you need.

  • \$\begingroup\$ i followed your suggestions and made simulation with LM324. first two stage opams didnt change their output but the last Schmitt trigger part I needed to update the resistors as 100k to haver a nice even pulse. What could be done? it seems like i do not need any capacitors or diodes? i.stack.imgur.com/H0I5L.png \$\endgroup\$
    – user16307
    Mar 31, 2015 at 11:39
  • \$\begingroup\$ i mean my problem is now this might work but for optimizing would i change resistor values ect? would you suggests 100k resistors instead. i cannot see the difference in simulations but in other perspectives i caouldnt decide \$\endgroup\$
    – user16307
    Mar 31, 2015 at 11:41
  • \$\begingroup\$ You will need power supply capacitors - use 10nF for each rail per quad op-amp and maybe a bulk capacitor of 10uF for each rail. If you are happy with the simulation, what resistor values do you think need changing and why. If you are going to design a circuit board there is always the possibility of resistor values changing due to "unforeseen problems" and simulation weaknesses. \$\endgroup\$
    – Andy aka
    Mar 31, 2015 at 13:32

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