Recently, I have started working on oscillators. I am trying to put forward a simple yet reliable voltage controlled Clapp oscillator (VCO). I have successfully demonstrated the oscillator operation. However, I would like to have more control over the frequency.
For this purpose, I am using a varactor capable of putting a capacitance varying between 5pF and 30pF. This allows me to pull the oscillator frequency from 25MHz + 7966Hz to 25MHz + 4193Hz.
What I want now is push down the fundamental oscillator frequency to (25MHZ - 2000Hz), so that with 4KHz frequency pulling up range, I could have control over the range between (25MHz - 2kHz) and (25MHz + 2kHz).
In other words, I am trying to achieve perfect 25MHz operation (i.e. 25.000.000Hz).
Next, the circuit topology I follow:
What can be added or removed from the circuit below to lower the fundamental oscillator frequency?
Thank you very much.