I have built a noise generator using a couple of CD4006 shift registers. The circuit is on page 9 of this PDF:
http://schematicsforfree.com/archive/file/Oscillators and Generators/Pink-White & Other Noise Generators/Pink & White Noise Generators - Misc.pdf
I used a CD4070 quad XOR instead of the older CD4030. I haven't implemented the pink filter or MPSA13 buffer, I'm just monitoring the output directly on the o'scope).
It is on breadboard and all works perfectly until I start varying the supply voltage, between 5V and 15V. It appears that at certain critical supply voltages (e.g. 5.3V, 10.0V and others...), the sequence stops being random and somehow gets stuck in a repeating pulse train of a few kilohertz, even though the clock continues to run normally. In fact, at 6.8V the output stays permanently low, yet the clock is running! Can anyone shed any light on this??
http://schematicsforfree.com/archive/file/Oscillators and Generators/Pink-White & Other Noise Generators/Pink & White Noise Generators - Misc.pdf
I used a CD4070 quad XOR instead of the older CD4030. I haven't implemented the pink filter or MPSA13 buffer, I'm just monitoring the output directly on the o'scope).
It is on breadboard and all works perfectly until I start varying the supply voltage, between 5V and 15V. It appears that at certain critical supply voltages (e.g. 5.3V, 10.0V and others...), the sequence stops being random and somehow gets stuck in a repeating pulse train of a few kilohertz, even though the clock continues to run normally. In fact, at 6.8V the output stays permanently low, yet the clock is running! Can anyone shed any light on this??