Dear Sougota,
You are possibly trying to use the Micro (PIC XXXXX) as part of the control loop to regulate the amplitude of your sine wave.
The alternbative approach is to build the control loop around SG 3524 PWM control IC & use you PIC XXXX micro to supply the set point to SG 3524.
SG 3524 will provide you with a very fast control action with minimum No. of components.
The point of using PIC micro in your application is to generate variable amplitude variable frequency sine wave using the PWM command in PIC Basic Pro.
You can also use a normal iron core transformer to check the results then convert to ferrite the ferrite core will icrease the effiiciency of your design.
A center tapped transformer is a good choice!!!
Reagrds.
Suded.