Amplifiers aim for accurate current sensing

Edited by the Electronicstalk editorial team Dec 16, 2004

National Semiconductor has expanded its high-performance precision amplifier portfolio with the addition of three high common-mode difference amplifiers.

National Semiconductor has today expanded its high-performance precision amplifier portfolio with the addition of three high common-mode difference amplifiers.

Designed for broad-based industrial, commercial and automotive applications, these new amplifiers meet the requirements for accurate current sensing measurements in products such as battery charging and discharging for notebook computers and cell phones, and fuel injection control.

The LMP8270 and LMP8272 high common-mode amplifiers and LMP8271 high common-mode bidirectional amplifier join National's LMP (linear monolithic precision) product family targeting the precision market.

"These three high-performance precision amplifiers allow National Semiconductor to serve a very important market segment", said Erroll Dietz, Vice President of National's Amplifier product group.

"National's new line of precision amplifiers delivers remarkable accuracy due to its very low offset voltage and drift".

"Also, because of their high input common mode voltage range, these parts are perfect for demanding applications, especially where current sensing is needed".

National's bidirectional LMP8271 measures charge and discharge currents at high common mode voltages typically found in precision applications.

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.

Accurate bidirectional load current measurements are achieved when monitoring the output with respect to the reference voltage.

National's LMP8270 and LMP8272 are unidirectional, fixed-gain, differential amplifier products.

These amplifiers will 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 to 27V input common mode voltage range and a supply voltage range of 4.5 to 5.5V.

These devices also function over an extended common mode input voltage (-5 to +36V), enabling high-side current sensing where the input voltage range far exceeds the supply voltage range of 5V.

The very low offset voltage (less than 250uV) and offset drift (less than 15uV/C guaranteed) of the LMP8270/71/72 allow for very accurate small input differential signal conditioning and minimal voltage offset error through the entire temperature range.

Additionally, the extended operating temperature range of -40 to +125C allows these amplifiers to be used in extreme conditions, such as those found in automotive and industrial applications.

National's new precision amplifiers are sampling now in limited quantities.

Available in SOIC-8 packaging, National's LMP8270 is priced at $1.45, the LMP8271 is priced at $1.57, and the LMP8272 is priced at $1.45, all in 1000-unit quantities.

The LMP8270, LMP8271 and LMP8272 will be available in full production in March 2005.