Product category: Analogue and Mixed Signal ICs
News Release from: National Semiconductor | Subject: LMP7721
Edited by the Electronicstalk Editorial Team on 19 March 2008
Precision amp shows little bias
Device yields maximum system sensitivity and accuracy from photodiode and high-impedance sensors.
The LMP7721 from National Semiconductor is a precision amplifier with the industry's lowest guaranteed input bias current (20fA) at room temperature and over the extended temperature range of -40 to +125C The device yields maximum system sensitivity and accuracy from photodiode and high-impedance sensors and is well-suited for improving sensitivity and accuracy in battery-operated portable applications, as well as electrochemical sensor interface circuitry
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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As a member of National's PowerWise family of energy-efficient products, the LMP7721 provides a wide gain bandwidth (GBW) of 17MHz while consuming only 1.3mA of current.
compared with competitive amplifiers that suffer an exponential increase of input bias current over higher temperatures, National's proprietary VIP50 BiCMOS process technology enables the LMP7721's input bias cancellation circuitry to maintain its low input bias current.
For example, the LMP7721 guarantees 900fA at 85C, which is 50% less than the closest competitive device.
Additionally, National provides a signal path solution for high-precision applications: analogue-to-digital convertors (ADCs) such as the 12bit ADC121S021and 14bit ADC141S626 are optimised to work with the LMP7721.
The LMP7721 precision amplifier provides 3fA, with a guaranteed limit of 20fA at 25C, 900fA at 85C and 5pA at 125C.
The amplifier also maintains ultralow input bias current over its entire input common-mode voltage range, and its wide GBW along with high open-loop gain of 120dB enables accurate signal conditioning.
Additional features of the LMP7721 include low input voltage noise of 6.5nV/(rt)Hz, low DC offset voltage of +/-150uV maximum at 25C and low offset voltage temperature coefficient of 1.5uV/C to improve system sensitivity and accuracy.
The LMP7721 has a supply voltage range of 1.8 to 5.5V and is offered in an 8-pin SOIC package with a special pinout that isolates the amplifier's input from the power supply and output pins.
This unique pinout further reduces system errors by preventing printed circuit board (PCB) leakage current from reaching the input pins.
By using the LMP7721 in place of an amplifier and discrete dual-input MOSFET, system designers can realise PCB space savings of approximately 50%.
The LMP7721 is available now and priced at US $4.95 each in 1000-unit quantities.
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