LFO signal prep to feed a VCA based on LM13700 OTA

This circuit takes an AC signal (likely from an LFO) that is 10vpp max acquiescent about gnd, runs through a clamp circuit to force the bottom peak of the signal at V--. Then the signal is buffered and finally converted to current via 5k resistor so that the output current is between 0-2 milliamps (between V++ and V--). This can be fed into the bias current pin of an LM13700 operational transconductance amplifier (OTA). Using this setup, the input signal amplitude can be set to 0 and the output should be steady 0 milliamps. The 100k resistor helps pull the clamp back to V-- when the amplitude is reduced. If the input is set to the max +5v/-5v amplitude, the output current will be between 0 and 2 milliamps. Haven't breadboarded this yet but according to the simulator, hopefully it will work.

published 9 years ago