@rocketracket The frequency will change either by shunt attenuating or Series R. both resulting in attenuation and frequency shift. But the FET AC drop distorts low freq. sine. while the Pot does not.
I still don't know what this is for and it is better with a PLL. If you value your time. Contact me.
For 1~200MHz, custom video design with current control is needed.
The 199 vs 200 difference inversely controls the Q and so 198 is faster but starts to clip. This was designed for 5V R-R output. The Cap can be tied to 5V or 10V. This gives a step pulse to one CAP to kick start Oscillator otherwise it takes a long time to grow to full swing.
This is not a custom design service site, but this design is custom from me.
Obvious choices are Op Amp or video amp with BW > 30MHz. e.g. LT6236CS6IC OPAMP GP 215MHZ RRO TSOT23-6
It regulates by going into saturation which reduces the gain to zero. Since gain or Pot R controls frequency, and amplitude of the integrator, the output adjusts to peak to peak swing. Naturally, a quick change in R changes gain momentarily over a 4:1 range, but the sine Vpp regulates according to matched feedback with <1% R mismatch gain for loop bandwidth or Q or clipping tradeoffs.
It is not intended for rapid FM but for pure sine as the Q is quite high for pure sine.
The other approaches
- Take any simple Relaxation triangle VCO and convert to sine , with bipolar triangle, using back-back LED or Zeners and R to regulate smooth linear to sine gain reduction curve after 2/3Vpp.
- any VCO into a counter with R,2R,4R,8R DAC or use 1 or 2 Johnson Counters with sine function weighted resistors. Cheap and Dirty Compute R values from Sine in Excel.
reverse engineer the FM sine gen, in a old Wavetek , HP or sim. Sig Gen,
Use 400MHz VCO and down convert