National Semiconductor has zero-drift op amps

Two zero-drift op amps from National Semiconductor provide a low input voltage noise (11 nV/sqrt Hz at a gain of 1000V/V) and high DC accuracy.

With these devices, the performance advantages of zero-drift amplifiers can be used in applications requiring high gain and low sub-15 nV/sqrt Hz noise.

The LMP2021 single and LMP2022 dual precision op amps are suitable for sensor interface applications including load cells and pressure and force sensors used in industrial systems, scientific weigh scales, medical and measurement equipment, and heating, ventilation and air conditioning (HVAC) systems.

Both devices are included in National's recently released Webench Sensor Designer tool.

National's zero-drift amplifiers use a noise-shaping technology that employs continuous-correction circuitry to auto zero the input offset error voltage.

This enables uninterrupted accuracy over time and temperature, with high common-mode rejection ratio (CMRR) and high power-supply rejection ratio (PSRR).

For example, as small amplitude input signals are amplified at higher gains, the input voltage noise of the op amps decreases from a typical 15 nV/sqrt Hz value, measured at a gain of 100V/V, to as little as 11 nV/sqrt Hz at a gain of 1000V/V.

Additionally, these op amps remove the undesirable 1/f voltage error component in low-frequency applications.

The LMP2021/22 feature integrated electromagnetic interference (EMI) suppression filters and join the recently released LMV83X, LMV85X and LMV86X EMI-hardened op amps.

The LMP2021/22 provides an EMI rejection ratio (EMIRR) of 79dB to reduce radio frequency (RF) interference from external sources.

Additionally, these op amps support 24-bit data acquisition systems and optimally drive National's ADC161S626 16-bit analogue-to-digital converter (ADC).

This ADC provides signal accuracy of +/- 0.003 per cent over the -40C to 85C temperature range.

In high-resolution data acquisition systems, designers commonly scale the output of a sensor to the full-scale input of the ADC to ensure optimum sensitivity.

The LMP2021 single and LMP2022 dual have only 0.004uV per deg C of input offset voltage drift (TCVos), with a typical Vos of 0.4uV.

Both devices operate across the 2.2V to 5.5V supply voltage range and offer a gain bandwidth (GBW) of 5MHz while consuming only 1.1mA of current per channel.

The LMP2021/22 op amps offer 160dB of open loop gain (AVOL), as well as performance exceeding 139dB for CMRR and 130dB for PSRR.

Both devices operate across the temperature range of -40C to 125C.

The LMP2021 is supplied in five-pin SOT23 and eight-pin SOIC packages, and the LMP2022 is supplied in eight-pin SOIC and eight-pin MSOP packages.

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