The DDC101 is a precision, wide dynamic range, charge digitizing A/D converter with 20-bit resolution. Low level current output devices, such as photosensors, can be directly connected to its input. The most stringent accuracy requirements of many unipolar output sensor applications occur at low signal levels. To meet this requirement, Burr-Brown developed the adaptive delta modulation architecture of the DDC101 to provide linearly improving noise and linearity errors as the input signal level decreases. The DDC101 combines the functions of current-to-voltage conversion, integration, input programmable gain amplification, A/D conversion, and digital filtering to produce precision, wide dynamic range results. The input signal can be a low level current connected directly into the unit or a voltage connected through a user selected resistor. Although the DDC101 is optimized for unipolar signals, it can also accurately digitize bipolar input signals. The patented delta modula-