# Getting square impulses from square wave input

I can't get this problem right... This problem was given by my professor as a possible exam question. I took a considerable amount of time thinking in it, but I'm yet unable to solve it. The problem is the following: Build a circuit that accepts a square wave as input and outputs a square impulse when the input reaches a rising edge(or at the falling edge, or in the middle of the square).

Since English is not my native language it may be better explained by this image:

So far the most complex circuit components we have learned are opamps and diodes(normal and zener).

I've tried everything I remembered but the closer I got was a simple impulse...

• In the middle is the hard part, if I said i had an idea involving current and a capacitor would that be too much of a clue? Maybe there are other ways? – George Herold Oct 24 '14 at 2:27
• The professor said the difficulty of the three setups is equivalent since once we get one right, the idea behind the others is the same. Until now the nearest I got(theoretically) was using an Integrator(forming a saw wave), followed by half-wave rectification and finnaly a diferenciator. But it fails since the integrator only returns positive values. – Miguel Horta Oct 24 '14 at 10:21