A method for charge balancing in a current input ADC including maintaining
a low capacitance value at the integrator output node where the
capacitance value is independent of the integrator output voltage and
operating conditions, generating a first voltage pedestal at a first
active device switch at the end of the autozero phase having a first
voltage polarity and a first magnitude, generating a second voltage
pedestal at a second active device switch at the end of the integration
phase having an opposite voltage polarity and the first magnitude, and
summing the first voltage pedestal with the second voltage pedestal. The
difference between the first voltage pedestal and the second voltage
pedestal results in a net voltage error. The first and second voltage
pedestals have the first magnitude under all operating conditions of the
modulator and the two voltage pedestals cancel to yield a small net
voltage error.