Pushing Down the Clapp Oscillator Frequency

by feineLinear   Last Updated July 11, 2019 22:25 PM

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:

enter image description here

What can be added or removed from the circuit below to lower the fundamental oscillator frequency?

Thank you very much.

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