bidrohini

You can take a look at the Klein Tools VDV512-101 Cable Tester.

You did a lot of hard work I must say. For this type of fading effect, I always use Arduino or AVR microcontroller. It is very easy to do this with the PWM pins of the Arduino. But making the project this much compact and without programming really needs good skills. Good work. 

You can add a decoupling capacitor. Sometimes, the output waveform can be clipped due to noise in the power supply. Adding a decoupling capacitor between the power supply and the ground can help reduce the noise and improve the output waveform.

Good to know that you got it working. 

I really like this circuit. Such a small and compact PCB.