The AD7785 is a low power， low noise， complete analog front end for high precision measurement applications. The AD7785 contains a low noise 20-bit ∑-Δ ADC with three differential analog inputs. The on-chip， low noise instrumentation amplifier means that signals of small amplitude can be interfaced directly to the ADC. With a gain setting of 64， the rms noise is 40 nV when the update rate equals 4.17 Hz. The device contains a precision low noise， low drift internal band gap reference and can accept an external differential reference. Other on-chip features include programmable excitation current sources， burnout currents， and a bias voltage generator. The bias voltage generator sets the common-mode voltage of a channel to AVDD/2. The AD7785 can be operated with either the internal clock or an external clock. The output data rate from the device is software-programmable and can be varied from 4.17 Hz to 470 Hz. The device operates with a power supply from 2.7 V to 5.25 V. It consumes a current of 400 μA typical and is housed in a 16-lead TSSOP package.