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Voltage controlled variable frequency audio oscillator schematic needed

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neazoi

neazoi

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Hi I need a variable frequency audio oscillator circuit that operates from 480Hz to 2700Hz. I do not care if it is square wave or sinewave (squarewave better).
What I do care is that the frequency can be varied with voltage and the output is around 50% duty cycle (not precisely critical).

I want to avoid any proprietary ICs. Discrete components or common ICs like the 555 are fine.

Can you please suggest me such a circuit?
Thank you
 
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    neazoi

    neazoi

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How to Build a Voltage Controlled Oscillator (VCO) with a 555 Timer Chip

In this project, we will show how to build a voltage controlled oscillator (VCO) with a 555 timer chip.
www.learningaboutelectronics.com

Much better linearity -


If you want 50% Duty Cycle on either of these use tiny gate logic D or T flip flop
to yield 50%.



Regards, Dana.
 

    neazoi

    neazoi

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The lm331 seems an excellent choice and it is cheap and readily available and in DIP.
Thanks a lot!
 

XR2206 & 2208 are 2 chips that would do this well if you are prepared to move away from a more discrete design
 

This VCO circuit is in the datasheet of the LM358 dual opamp:
 

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