Sine

[Electronman]

ok thanks for all inputs,

assume I use another low pass filter to convert the Ramp to the sine, then how can I cause it to oscillate at 6kHz and 8V?

 

[audioguru]

The value of the capacitor and the resistor that drives it in the square-wave oscillator determines the frequency.
the supply voltage and how you filter it determines the amplitude.

 

[Electronman]

dougy83,

I prefer your idea by adding another RC low pass filter to my circuit, but please tell me how to get 6khz and 8V with this mode?

thanks

 

[Electronman]

The value of the capacitor and the resistor that drives it in the square-wave oscillator determines the frequency.
the supply voltage and how you filter it determines the amplitude.

Thanks but any formula?

 

[audioguru]

If the values of R1 and R2 are higher then the output of the opamp will not be overloaded like it is now and the frequency calculation will be more linear with changes in the values of R2 and C2.

 

[dougy83]

Thanks but any formula?

the corner frequency (0.707 of the passband amplitude) is at f = 1/(2*pi*r*c)

Pick a frequency a fair bit lower than the sinewave frequency as these filters have low performance. Getting 8V amplitude will be very hard as the RC filters attenuate the signal significantly.

 

[mneary]

You can do this without adding components if you are allowed to rearrange them. Look up Wein Bridge oscillator. If you are allowed to add one capacitor you can make a phase-shift oscillator.

 

[colin55]

By simply changing the value of R1 and C1, the output will turn into a waveform very similar to a sinewave.