I am experimenting with noise (synth drum sounds). I built this 4069 noise generator. Noise is generated as expected...but it generate a hum sound. First I built it on a breadboard...noise and hum ....since it is very simple I built it (on a small perforate board and solder the components)....noise and hum again....how can I do to get rid of the hum?
To answer ljcox - I am operating it with a 9V battery. No I dont have the capacitor bypassing . Do I need two capacitors, both from + and GND?
To Hero999 - I found this on a Patent circuit , so I give a try, and it work...well beside the hum.
To answer ljcox - I am operating it with a 9V battery. No I dont have the capacitor bypassing . Do I need two capacitors, both from + and GND?
To Hero999 - I found this on a Patent circuit , so I give a try, and it work...well beside the hum.
The attachment shows an example of one of these oscillators.
They are also mentioned in the National Semiconductor Data Book (that I was given many years ago) together with the maths necessary to calculate the frequency of oscillation. I can scan a page or two if you wish.
A normal inverter can't be used as an oscillator on its own, there needs to be two or more stages.
A normal inverter will go into the linear region when a resistor is connected between the input and output and stabilise at roughly half the supply voltage.
A Schmitt trigger has no stable state so will oscillate if a resistor is connected between the output and input.
To build an oscillator with the CD4069, you need to use two gates.
This circuit is not an oscillator, it's a linear amplifier, the idea seems to be to amplify the noise generated by the first stage 100 times but it doesn't seem to work because the ambient 50/60Hz mains hum is much stronger than the noise generated inside the IC.
I did a Google search for 4069 oscillator and a host of results appeared.
I could not find one as in th OPs circuit, but there are single inverter LC & Crystal oscillators. I've attached an example.
However, I think you're right about doing it with a single inverter as in his circuit because I can't see how you can get 180 degrees phase shift with a single RC.
Its just that I have a vague recollection that I've seen it done.