High-precision Programmable Gain Amplifier
National Semiconductor introduced what is said to be the industry’s highest-precision programmable gain amplifier (PGA) for sensor interface applications and data acquisition systems targeting the industrial and instrumentation markets. The LMP8100A provides 0.03 percent gain accuracy using a software adjustable gain (in 1V/V increments) from 1V/V to 16V/V over the full industrial temperature range of -40°C to 125°C. The company also offers the LMP8100 semi-precision grade PGA, which provides 0.075 percent gain accuracy over the -40°C to 125°C temperature rage. The amplifier’s closed-loop gain is set by an array of 16 precision thin-film resistors. At the core of the PGAs is a precision 33 MHz CMOS input, rail-to-rail, input/output (RRIO) operational amplifier with a typical open-loop gain of 110 dB. The LMP8100A provides four levels of internal frequency compensation, which at the higher gain settings increases the usable signal bandwidth. Its input zero calibration feature allows the user to measure the output offset voltage to calibrate any errors resulting from temperature or voltage shifts. The amplifier’s control modes are programmed via a serial port that also allows several devices to be cascaded, permitting an array of LMP8100 amplifiers to be programmed by a single microcontroller serial data stream.