Yes..we can use Analog signal in digital system
For this we need to convert Analog signal into Digital signal.
Because digital system works only with digital signals.
1.Using SAR (Succesive Approximation Register) method we can convert analog signal into digital signal.
This method provides most accurate digital signal for the given analog signal.
Analog signal is converted to digital signal by comparing the analog input with reference voltage which are given to comparator and corresponding digital signal is obtained as output from the comparator