What Sine-Wave Oscillator can be controlled with a microcontroller?
I need a Sine Wave Oscillator circuit that can allow me to control its frequency with a microcontroller. Until now all the topologies that I have found if the frequency is changed, a change in the circuit component is mandatory here is some topologies:
Courtesy of TEXAS INSTRUMENTS
For now am going to be using Arduino as a microcontroller, some forums suggest the use of AD9850 module but I couldn't find it :( .
The frequency range that I am aiming is from 10 Hz to 10 MHz pure stable sinusoidal wave. And the amplitude of 10 Vpp ,1 mA , -28 dBc (if my calculation is correct), the two ways that i can think of to control the circuit is with the help of a digital potentiometer or a DAC of 8 bit or 12 bit.
So i have found this circuit which is based on Varactor a VCO;
My question is why we need a DC isn't the AC enough?