Difference Amps Claim Accuracy Benchmarks April 2005 Issue Published Date: April 04, 2005
Promising to redefine accuracy in current-sensing applications, the bidirectional LMP8271 and unidirectional LMP8270/LMP8272 high common mode difference amplifiers target industrial, medical and automotive applications. The LMP8271 measures charge and discharge currents using an external reference voltage to set a zero-current condition. An output voltage greater than the reference indicates a charging current condition while an output below the reference identifies a discharging condition. Bidirectional load-current measurements are achieved when monitoring the output with respect to the reference. The LMP8270 and LMP8272 fixed-gain devices detect, amplify, and filter small differential signals in the presence of high common mode voltages. For the LMP8270 and LMP8271, gain is fixed at 20, and for the LMP8272 gain is fixed at 14. Features common to all three include 4.5V to 5.5V operation, a -2V to 27V input common mode voltage range, an offset voltage of less than 250 µV, offset drift of less than 15 µV, and an operating temperature range from -40°C to +125°C. Prices for the LMP8270, LMP8271, and LMP8272 are $1.45, $1.57, and $1.45 each/1,000, respectively. NATIONAL SEMICONDUCTOR, Santa Clara, CA. (800) 272-9959.
