0

I am trying to build a circuit which toggles a lamp on and off. I am using a JK flip-flop for the toggling action.

I want a clock pulse of 1 Hz. I know there are many ways to generate a clock pulse, but I want to generate it using a Schmitt trigger using an op-amp.

Current pick of components is 74LS109 for a ("TTL-level") JK flipflop and LM741 as the Op amp, supplied with 15 V, -V connected to GND.

Please let me know if it's possible or not, and if possible, what the circuit parameters should be.

Any other way of generating a clock signal using an op-amp would also be appreciated.

greybeard
  • 1,469
  • 1
  • 4
  • 17
Jina
  • 81
  • 6
  • What's the maximum allowed rise/fall time for the flip flop's input? – Andy aka Feb 05 '23 at 10:47
  • The trick is to produce voltage levels suitable for the FF: what voltages is the power supply for the op-amp? – greybeard Feb 05 '23 at 10:54
  • The power supply for the op-amp is 15 V DC – Jina Feb 05 '23 at 10:56
  • IC 74LS109 JK flipflop IC, supply of Op amp is just 15 V the negative Vcc pin is grounded. LM741 is the Op amp IC. – Jina Feb 05 '23 at 11:08
  • (TI's LS109 datasheet: *clock triggering occurs at a voltage level and is not directly related to clock pulse rise time* (my 2c: Schmitt trigger input (while the schematic doesn't look the type)).) – greybeard Feb 05 '23 at 12:23
  • 1
    Why do they even _manufacture_ [LM741](https://electronics.stackexchange.com/questions/304521/reasons-not-to-use-a-741-op-amp) anymore? We managed to eradicate smallpox. – pipe Feb 05 '23 at 17:51

1 Answers1

0

The 741 will need a lot more components. You could do a classic op amp oscillator with an op amp that swings to the ground rail. Then using a ultra-low VF Schottky barrier diodes the cathode could be the input to the LS device. Reason the max voltage for LS is about 0.8V or less for it to see a low. The inputs when open are high. I would not trust this over temperature.

If it were me I would use something like a 74C14 (I have not done this with a 74LS device) then place about 10uf to ground on the input with maybe a 200K from output to input. These are just starting values. You could also add a trimmer in the feedback loop to adjust frequency.

Gil
  • 4,951
  • 2
  • 12
  • 14