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Single supply VCO CIRCUIT

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paulmdrdo

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I have this VCO circuit taken from the net. I build the circuit in LTspice and It works perfectly fine but I want to change the frequency of the signal output. Basically what I wanted to do is to have a signal that is going above and below a center frequency by 4khz with a sensitivity of 1khz/v.
For example, Fc = 132khz, Fmin = 128khz, Fmax = 136khz. I just want to know what components should I change in my circuit. A formula would be helpful If anyone here is familiar with the circuit. Thank You! Single-Supply Op Amp - Comparator Voltage-Controlled Oscillator-schematic.pngSingle-Supply Op Amp - Comparator Voltage-Controlled Oscillator-schematic.png
 

Hi,

I'm not familiar with this circuit.

A quick view lets me assume that C_int is responsible for the (center) frequency.

Add a series resistor (in the Megaohms range) to the control_voltage_input to adjust for the V-f rate.
In case this increased resistor moves your center frequency then try to add a capacitor (maybe 100nF) from left side of R3 to GND.

Klaus
 

KlausST said:
Hi,

I'm not familiar with this circuit.

A quick view lets me assume that C_int is responsible for the (center) frequency.

Add a series resistor (in the Megaohms range) to the control_voltage_input to adjust for the V-f rate.
In case this increased resistor moves your center frequency then try to add a capacitor (maybe 100nF) from left side of R3 to GND.

Klaus
Click to expand...

I shifts the frequency but only slightly. here's an online simulator https://www.multisim.com/content/kK...omparator-voltage-controlled-oscillator/open/
 

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