flip-flop circuit

[yalect]

Hi,
I would like to ask you if I can build flip-flop led ciruit using op-amp Lm358 and what it's Working conditions?
Thank you

[GerryR]

I am reasonably sure that if you google "op-amp flip-flop," you will only find about a million, + or -, versions of op-amp flip-flops!  As an example:  https://www.radiolocman.com/shem/schematics.html?di=463517.  Adapting the 358 should be pretty straight forward. 

[yalect]

thank you for your reply
but Features of LM358 allow to make flip-flop circuit?

[David Hess]

Yes, an LM358 will work fine in a flip-flop circuit.

[Zero999]

Coincidentally, I've just been working on a schematic which requires an op-amp bistable. I chose the comparator, rather than an IC or discrete bistable, because the trigger voltage can be set fairly accurately.

Here's the circuit, but using the LM358 and changed so I can post it here. The original design uses an LM393 comparator and is part of a bigger design. If Schottky diodes are used, the forward voltage can be ignored for most applications and the bistable will fire when the inputs are above V2. Using high values for R1 and R2, reduces the errors from the diode forward voltage, but increases the errors from the diode leakage and op-amp bias currents. Adding resistors with the same values as R1 and R2 in series with the non-inverting inputs will minimise the latter.

R3 and C1 form a power on reset circuit, which ensures it always starts up in the same state when power is first applied.

[yalect]

Hi,
thank you
- I think your circuit based on two part of LM358 not one, why not like following, may it will works?

[Zero999]

Hi,
thank you
- I think your circuit based on two part of LM358 not one, why not like following, may it will works?

That's an astable, i.e. oscillator, rather than a bistable.

Yes, a monostable can be made with just one op-amp, but there are advantages with using two (see my previous post) and if the other op-amp in the LM358 is spare, you might as well use it for something.

[yalect]

Hi,
 - I would like to ask you what the aim of using pulses
in my post for single LM358 part it generates pulses itself,
- as such circuits, there are conditions for the three resistors and C?
thank you

[Zero999]

Hi,
 - I would like to ask you what the aim of using pulses
in my post for single LM358 part it generates pulses itself,
- as such circuits, there are conditions for the three resistors and C?
thank you

Your original post is ambiguous. You didn't say what sort of flip-flop circuit you're looking for, so people just assumed bistable, since it's the default meaning of the word flip-flop. There are also monostable (timer) and astable (oscillator) circuits and it now appears you require the latter.

The resistor values in my circuit are not critical. If you read the post again, you'll find I hinted on the advantages/disadvantages of using higher/lower values. Please ask specific questions.

[Ed.Kloonk]

Hi,
 - I would like to ask you what the aim of using pulses
in my post for single LM358 part it generates pulses itself,
- as such circuits, there are conditions for the three resistors and C?
thank you

Your original post is ambiguous. You didn't say what sort of flip-flop circuit you're looking for, so people just assumed bistable, since it's the default meaning of the word flip-flop. There are also monostable (timer) and astable (oscillator) circuits and it now appears you require the latter.

The resistor values in my circuit are not critical. If you read the post again, you'll find I hinted on the advantages/disadvantages of using higher/lower values. Please ask specific questions.

I thought he might have been talking about going for a jog around a beach suburb wearing thongs. (footwear)

 

[GerryR]

The OP should have enough info from the above posts to figure out the rest of what he needs by himself.  I was told once not to do a poster's homework for him; heck the whole project was done for him a couple of times.  Just saying.