Filter designer software complements op amps

Staff -- Test & Measurement World, 2/1/2005

National Semiconductor has expanded its precision amplifier portfolio with the addition of three high-common-mode difference amplifiers and has complemented them with its WEBENCH Active Filter Designer online simulation software. The bidirectional LMP8271 measures charge and discharge currents at high common-mode voltages. It uses an external reference voltage to set the voltage defining a zero-current condition. An LMP8271 output voltage greater than the external reference voltage indicates a charging current condition while an output voltage below the external reference voltage identifies a discharging current condition.

The LMP8270 and LMP8272 are unidirectional, fixed-gain, differential amplifiers that detect, amplify, and filter small differential signals in the presence of high common mode voltages. For the LMP8270 and LMP8271, the gain is fixed at 20. For the LMP8272, the gain is fixed at 14.

These parts have a –2-V to 27-V input common mode voltage range and a supply-voltage range of 4.5 V to 5.5 V. Offset voltage less than 250µV and offset drift less than 15 µV/°C allow for accurate small-input differential signal conditioning and minimal voltage-offset error.

WEBENCH Active Filter Designer is an online simulation tool that speeds the creation of sophisticated filters for data-acquisition and signal-conditioning applications using amplifiers such as the new LMP8270.

Price: amplifiers, from $1.45 each in quantities of 1000. Production quantities available in March. Use of WEBENCH Active Filter Designer is free; registration is required. National Semiconductor, Santa Clara, CA. www.national.com.