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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I need a logic circuit, with 2 inputs and 1 output, that will do the following: 1) Falling edge on input 1 makes the output HIGH. 2) Falling edge on input 2 makes the output LOW. The rising pulse as well as both inputs going low/both high simultaneously, must not affect the output. It can be rising edge triggered too, I just put inverters before the inputs. I heard of "D-type flip flop" circuits but I've read the data sheet and have no idea how to implement it.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
A two-transistor bistable multivibrator (flip-flop) is all you need - Google. Even Wikipedia gives the answer ! (bottom of page) You'll need one capacitor for the SET base and one for the RESET base.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Sulaiman, I tried that multivibrator with caps between inputs and the bases, but the problem is that as one of the inputs goes HIGH, it turns the corresponding transistor ON again by applying positive pulse on its base. In other words, it is not usable for my application.
Or did you mean to put the caps in in a different way?
Registered Member #347
Joined: Sat Mar 25 2006, 08:26AM
Location: Vancouver, Canada
Posts: 106
Two edge detectors and a SR flip flop would do what you want. Connect each input to falling edge detector, and connect both of those outputs to the set and reset connections on the flip flop. See the attached picture.
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Logic circuit
