I'd like to control the pulse with modulation of a VCO with an external oscillator (triangle wave). The PWM circuit is a comparator fed with the triangle wave output of the VCO. The VCO schematic is a classic design taken from the datasheet.
I'm trying to control the pulse width using a JFET used as a variable resistor, but the output of the JFET the result is a strange behavior of the CV, a triangle wave followed by a continuous voltage like in the screenshot attached (in yellow the original CV signal and in light blue the output of the JFET).
I don't know how to go on... anyone could help me to resolve the problem? Thanks!