5V logic tester

elektor july/august 1983 94 1~ C. Bajeux 5 V logic tester The full title for the description of this circuit should be "3 state 5 V logic tester", which at least hints at the fact that this logic tester is something out of the ordinary. And indeed it is, for not only does it differentiate between the two normal logic levels (high and low) but also it indicates when the signal under test is neither of these, be it a negative voltage, more than 5 V or even an alternating voltage. Si milary it recognises unpolarised TTL or LS circuit in puts. And that is not all ..., this circuit also enables the logic level indication to be made audible, so there is no need to concentrate on anything other than the circuit under test. To do all this the circuit uses an LM 3914, which is an IC that can sense analogue voltage levels and can directly drive 10 LEDs to pro- vide a linear 10 step disp The IC, among other tF its own adjustable refere that controls the intern divider chain. The refer (at pi...