Voltage Controlled LFO

Posted on Feb 6, 2014

This is a nice LFO for all of your modulation needs. The frequency can be voltage controlled to add a new dimension to your sound palette. The pulse width of the rectangle wave can be varied between approximately 10% and 90% again lending variability to the modulation capabilities of this LFO. Voltage control can be used to vary the pulse width as

Voltage Controlled LFO
Click here to download the full size of the above Circuit.

well. If you power your circuits with +/-15 volts then observe the recommended changes that are noted on the schematic. I recommend a complete review of this page before buying a board. U1 and associated components comprise a linear voltage to log current converter. The current flowing into the collector of Q2 controls the current flowing from the bias input of U3-A transconductance amp to ground via Q3. The transconductance of U3-A is used to control the frequency of the oscillator. U2-A and associated components comprise an integrator. When current flows into U3-A`s output the integrator ramps up and when current flows out of U3-A`s output the integrator ramps down. When the integrator`s output goes above the threshold of comparator U4-A and associated components it`s output goes high (to near +V). The output of U4-A is fed to the non-inverting input of U3-A transconductance amp. While U4-A`s output is high current flows out of U3-A`s output and the integrator ramps down until the voltage at the input of U4-A goes low enough to overcome the hysteresis provided by R18 and it`s output goes low. When this happens the comparator starts to ramp up again and thus we have a triangle wave at the output of U2-A. The amp bias of U4-A is controlled by the current generated by the linear voltage to log current convertor. This controls the current that flows in and out of U4-A and thus the frequency of the oscillator. The...

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Current Limiting Power Supply
    Lamp Flasher
    Solar Garden LED Lighting
    Super Motion Sensor Ultrasonic Motion Detector
    Bicycle Back Safety Light Circuit Schematic Circuit
    Search Light Signal
    laser diy schematics
    Simple RF Detector For 2M
    Simple battery charger circuit and battery level indicator with low battery recharge alarm
    Lx1995 Led Driver: Camera Flash Application
    GOL tremelo project
    Audio Mixer
    Automatic light control circuit curtains
    Press light switch double circuit
    Frequency electronic locks LM567 schematic
    Automotive electronic locks circuit