Dear Kai,

Thanks for your kind reply,

The solution you have given is very good, since the headache of signals running from Digital plane to Analog plane is not needed. [ It was surely required with Analog / Mechical switch method ].

I could understand the purpose of the lower two sections of the schematic you have posted. The middle one is 1.5 times non inverting amplifier and the last one is 3 times non inverting amplifier. But what exactly does the first one do. Kindly let me know. Also please tell me can I use the schematic as is or some modification is needed for practical implementation.

Thanks for your continous kind support.

Regards,
Prahlad Purohot