Hi everyone!
I wanted to share this rather simple schematic that I came up with. It is a VCLFO that can be built using only one TL074 IC. I haven't seen it done this way, but then again I haven't seen all the designs that are out there. Or maybe there is a reason why it should not be done this way. I am sure someone will point it out if that is the case.
I have breadboarded it and it seems to work wonderfully. In the configuration shown in the schematic it has a range of ~0.09Hz to 16Hz . You get two waveforms - triangle and square.
This is a voltage controlled, voltage driven oscillator. U1.2 with help of Q1 and the signal from U1.4 switches between the control voltage and inverse of it that goes to the integrator. Voltage to U1.2 is supplied from U1.1. U1.1 does two things - it combines the control signals and with help of D1, R1 and R2 keeps its output from reaching 0v. Reference voltage at U1.1 non-inverting input should be greater than the voltage drop of D1 to keep U1.1 output always negative. If U1.1 output reaches 0v LFO stops oscillating. You can substitute R1 and R2 with a trimpot to dial in the precise voltage that you need. It will let you get closer to the 0v and thus make it oscillate slower on the low end.
Easiest way to change the range of this LFO is by changing C1 and R9.
VCO:
This circuit can also be pretty easily made into a 1v/oct VCO. All you have to do is change C1 to something smaller like 1.5n, change Q1 from PNP to NPN and make U1.1 into current to voltage converter and connect it to exponential converter. I have not tested it this way but I have made similar VCO in the past. The biggest difference between this and the one I built is that the one I built uses a SPDT switch IC for switching between the control signal and inverse of it. But the main idea is pretty similar and it works pretty well.
While it will work as in schematic you should probably change R11 and R14 so that the charge and discharge times are smaller. As in the schematic it is set so that the triangle output is ~10vpp but it severely limits the range of the VCO. You will have to bring the triangle signal back up to 10vpp elsewhere if you change R11 and R14.
Thank you for your attention and hope this helps someone!
I wanted to share this rather simple schematic that I came up with. It is a VCLFO that can be built using only one TL074 IC. I haven't seen it done this way, but then again I haven't seen all the designs that are out there. Or maybe there is a reason why it should not be done this way. I am sure someone will point it out if that is the case.
This is a voltage controlled, voltage driven oscillator. U1.2 with help of Q1 and the signal from U1.4 switches between the control voltage and inverse of it that goes to the integrator. Voltage to U1.2 is supplied from U1.1. U1.1 does two things - it combines the control signals and with help of D1, R1 and R2 keeps its output from reaching 0v. Reference voltage at U1.1 non-inverting input should be greater than the voltage drop of D1 to keep U1.1 output always negative. If U1.1 output reaches 0v LFO stops oscillating. You can substitute R1 and R2 with a trimpot to dial in the precise voltage that you need. It will let you get closer to the 0v and thus make it oscillate slower on the low end.
Easiest way to change the range of this LFO is by changing C1 and R9.
VCO:
While it will work as in schematic you should probably change R11 and R14 so that the charge and discharge times are smaller. As in the schematic it is set so that the triangle output is ~10vpp but it severely limits the range of the VCO. You will have to bring the triangle signal back up to 10vpp elsewhere if you change R11 and R14.
Thank you for your attention and hope this helps someone!
Statistics: Posted by John — Sat Oct 19, 2024 10:54 am — Replies 2 — Views 122