flip-flop circuit - Page 1
Forum section: electronics / beginners

author: yalect
author_rank: Regular Contributor
timestamp: February 12, 2020, 10:44:55 am
content: Hi,I would like to ask you if I can build flip-flop led ciruit usingop-amp Lm358and what it's Working conditions?Thank you

author: GerryR
author_rank: Frequent Contributor
timestamp: February 12, 2020, 11:52:18 am
content: 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.

author: yalect
author_rank: Regular Contributor
timestamp: February 12, 2020, 03:01:10 pm
content: thank you for your replybut Features ofLM358allow to make flip-flop circuit?

author: David Hess
author_rank: Super Contributor
timestamp: February 13, 2020, 02:25:12 am
content: Yes, an LM358 will work fine in a flip-flop circuit.

author: Zero999
author_rank: Super Contributor
timestamp: February 13, 2020, 04:12:09 pm
content: 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.

author: yalect
author_rank: Regular Contributor
timestamp: February 14, 2020, 11:32:29 am
content: Hi,thank you- I think your circuit based on two part ofLM358not one, why not like following, may it will works?

author: Zero999
author_rank: Super Contributor
timestamp: February 14, 2020, 02:55:07 pm
content: Quote from: yalect on February 14, 2020, 11:32:29 amThat'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.

author: yalect
author_rank: Regular Contributor
timestamp: February 14, 2020, 09:31:10 pm
content: Hi,- I would like to ask you what the aim of using pulsesin my post for single LM358 part it generates pulses itself,- as such circuits, there are conditions for the three resistors and C?thank you

author: Zero999
author_rank: Super Contributor
timestamp: February 16, 2020, 08:50:45 am
content: Quote from: yalect on February 14, 2020, 09:31:10 pmYour 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.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: February 16, 2020, 09:50:21 am
content: Quote from: Zero999 on February 16, 2020, 08:50:45 amI thought he might have been talking about going for a jog around a beach suburb wearing thongs. (footwear)

author: GerryR
author_rank: Frequent Contributor
timestamp: February 16, 2020, 12:55:45 pm
content: 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.