can yoy explain the working principle of IC7107?

Answer 1

It is an analog-to-digital converter. It most likely uses a dual-slope method of A/D conversion. It also has the digital logic to convert the count output of the dual-slope converter to binary-coded-decimal (BCD) to drive 3-/2 seven-segment displays (thats 3 least significant digits and the most-significant digit that only registers as 0 or +/-1).

The dual slope converter works like this:
The analog voltage to be measured is impressed onto an comparator while an integrator starts to 'ramp' up. At the same time a counter starts. When the integrator voltage is equal to the input voltage the comparator switches and turns the counter off. This count is a representation of the input voltage, knowing the time constant of the integrator and the count frequency.

To make sure the integrator did not have any residual charge at time-zero, the integrator is now discharged at a very precise rate, while the counter counts down. When the charge on the integrator capacitor reaches zero, the count difference from its max value to the current count must be a fixed number (due to the precise time (slope) it takes to discharge the integrator). Any remainder to that difference represents an error (initial charge or leakage in the integrator) and is corrected digitally in the readout.

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Answer 2

You'll need to be more specific as to the manufacturer and prefix. If you're referring to generic ECG for instance, it's a power switching regulator. However, this may be completely different from another manufacturer.

Answer 3

Intersil ICL7107 ?