Power Electronics

Precision Low-voltage Amplifiers Based on BiCMOS Process

Six operational amplifiers from National Semiconductor Corp. are built on its proprietary VIP50 process technology. These devices feature significant improvements in accuracy, low power consumption and voltage noise for industrial, medical and automotive applications. These improvements, combined with the products’ small size, also make them suitable for portable applications. The LMV651, LMV791, LPV511 and LPV7215 are National’s four latest low power, low-voltage amplifiers. Product features include 12-MHz unity-gain bandwidth, functional operation up to 12 V and 6.6 µs propogation delay time. National also is introducing the LMP7701 and LMP7711, the first products in a series of next-generation operational amplifiers that offer higher performance, sub-300 µV and sub-150 fA of input offset with guaranteed input bias of less than 200 fA, and up to 12-V operation.

The LMP7711 single amplifier offers low current (50 fA) metal oxide silicon (MOS) inputs while still providing low-noise (less than 7 nV/sqrt Hz) performance, minimizing distortion and signal conditioning errors. Precision thin-film resistors and well-matched transistor pairs are used to guarantee input offset errors of less than 200 µV, increase common-mode rejection ratio (CMRR of 95 dB) and increase power supply rejection ratio (PSRR of 100 dB) performance, while maintaining a low offset voltage drift (TCVos) of 1 µV/°C over extreme temperatures (-40°C to 125°C). The LMP7701 precision amplifier operates from 2.7-V to 12-V supply voltages and has rail-to-rail CMOS inputs with low input-bias current (200 fA). Trim and design techniques eliminate the large offset glitch associated with conventional CMOS rail-to-rail input amplifiers, improving the input offset voltage of less than 300 µV across the entire common-mode voltage range (0 V to 12 V). It also employs a patented correction technique to reduce the large temperature coefficient of the offset voltage commonly found in CMOS precision amplifiers. Both products are available in a SOT23 package.

The LMV791 low-noise CMOS input operational amplifier offers 5.8 nV/sqrt Hz of flat band noise. Its low offset voltage of less than 1.3 mV and low temperature coefficient of less than 3 µV/°C improve overall system accuracy. The 100-dB PSRR and 95-dB CMRR provide the dc performance needed in high-performance applications. A shutdown feature reduces power consumption to less than 1 µA when in idle mode. The LMV791 is available in a 6-lead TSOT23 package.

The LMV651’s high-efficiency design provides 90% power savings over previous-generation operational amplifiers by consuming only 115 µA while maintaining a 12-MHz unity-gain bandwidth and a low 1/f noise voltage of 17 nV/sqrt Hz. Overall dc system accuracy across various input voltages and supply voltages is improved by an input offset voltage below 1 mV, 100-dB CMRR and 95-dB PSRR. The LMV651 is offered in an SC70 package.

The LPV511 micro-power operational amplifier and the LPV7215 micro-power comparator consume less than 900 nA and 600 nA of supply current, respectively. Both products offer rail-to-rail inputs and outputs. The LPV511 is specified for 2.7-V to 12-V operation, while the LPV7215 comparator is operational from 1.8 V up to 5 V. The LPV7215 offers a 6.6-µs propagation delay. The space-saving SC70 package makes these products suitable for continuously on, battery-powered applications, such as smoke detectors, as well as industrial, telecommunications and automotive applications.

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