The DDC114 is a 20-bit quad channel, current-input analog-to-digital (A/D) converter. It combines both current-to-voltage and A/D conversion so that four low-level current output devices, such as photodiodes, can be directly connected to its inputs and digitized. For each of the four inputs, the DDC114 provides a dual-switched integrator front-end. This design allows for continuous current integration: while one integrator is being digitized by the onboard A/D converter, the other is integrating the input current. Adjustable full-scale ranges from 12pC to 350pC and adjustable integration times from 50s to 1s allow currents from fAs to As to be measured with outstanding precision. Low-level linearity is 0.5ppm of the full-scale range and noise is 5.2ppm of the full-scale range.