Up/down clock generator

up/down clock generator 154 1 R7 Various designs of clock generators have appeared in previous Summer Circuits issues of Elektor Elec- tronics, and this tradition is kept up with the present design which, un- like the other circuits, outputs an up/down indication as well as a rec- tangular signal over a wide fre- quency range; 0 Hz to several kHz. The output signal and the U/D indi- cation are both controlled by a single potentiometer. If this is set to the centre of its travel, nothing happens; turning the potentiometer in the clockwise direction causes the U/D output to be at logic high level, and the frequency of the output signal rises with turning Pi further in this direction. The same goes for turning it anti-clockwise, U/D being at low logic level. The basic operation of the circuit is as follows. Operational amplifiers Ai and A2 together constitute a sawtooth/square wave generator. The falling edge of the sawtooth voltage has a fixed duration of about 200 kis, as defined b...