HexInverter
New Member
Hey guys!
I am hoping someone will be able to assist me with this circuit.
I am looking to control the rate of discharge from a capacitor with voltage. I have tried to implement a voltage-controlled current sink as per the LM3900 Norton Amplifier datasheet:
In essence, I want to be able to voltage control the rate of decay of a simple voltage envelope generator made by charging and discharging a capacitor.
Ideally,
Less voltage = longer discharge
More voltage = faster discharge times
I experimented with this circuit a bit without the capacitor and got consistent results from 0mA to approximately 10.5mA when using 0-12V voltage control, all good so far! That was measured with my multimeter.
But, when I connected the capacitor and charged it, then used the LM3900 to sink current from it, all sorts of interesting behaviour happened. The LM3900 seems to discharge the capacitor to a certain voltage, and then stop. I can vary the end voltage it discharges to by varying the voltage input.
Can anyone shed some light on what is happening here, or what I am doing wrong?
Thanks so much for any help
I am hoping someone will be able to assist me with this circuit.
I am looking to control the rate of discharge from a capacitor with voltage. I have tried to implement a voltage-controlled current sink as per the LM3900 Norton Amplifier datasheet:
In essence, I want to be able to voltage control the rate of decay of a simple voltage envelope generator made by charging and discharging a capacitor.
Ideally,
Less voltage = longer discharge
More voltage = faster discharge times
I experimented with this circuit a bit without the capacitor and got consistent results from 0mA to approximately 10.5mA when using 0-12V voltage control, all good so far! That was measured with my multimeter.
But, when I connected the capacitor and charged it, then used the LM3900 to sink current from it, all sorts of interesting behaviour happened. The LM3900 seems to discharge the capacitor to a certain voltage, and then stop. I can vary the end voltage it discharges to by varying the voltage input.
Can anyone shed some light on what is happening here, or what I am doing wrong?
Thanks so much for any help