Programmable gain amplifiers and multiplexers combined

Integration is the name of the game with Texas Instruments latest programmable gain
amplifiers (PGA). Destined for microprocessor-based applications such as portable data acquisition, remote meter reading, automatic gain control and handheld test equipment, the PGA11x family's integrated multi-channel multiplexers (MUX) provide calibration and digitally controlled gain, enabling design engineers to accurately match the sensor output to an analog-to-digital converter (ADC) input voltage range.

The PGA112 and PGA116 offer binary gains of 1, 2, 4, 8, 16, 64, and 128 while the PGA113 and PGA117 have scope gains of 1, 2, 5, 10, 20, 50, 100 and 200. The PGA112 and PGA113 have a two-channel MUX and come in a MSOP-10 package, and the PGA116 and PGA117 have a ten-channel MUX and are available in a TSSOP-20 package. TI says that the op amp output stage can be powered by the same power supply as the ADC, which is useful in multi-supply systems to prevent an
over-voltage/lockup condition on an ADC input.

Gain switching time is 200ns, whilst gain settling is 2.55s at 0.01 percent. For all of the devices, DC gain error is 0.1 percent (max with G less than or equal to 32) over
temperature. All devices use a standard SPI serial interface with daisy-chain capability, and there are internal calibration channels for all of the PGA11x family.

Other features include an offset of 100uV (max) and an offset drift of 1.2uV/C (max), low noise (1nV/rtHz typical) and wide bandwidth (10MHz in G=1). In addition, the devices feature low input on-channel current (5nA max) and shutdown that can achieve a supply current of less than 4uA (typical). The PGA11x family is also specified over an extended temperature range of -40C to +125C.

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