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A hat-trick of op-amps

National Semiconductor has introduced three operational amplifiers (op amps) with integrated electromagnetic interference (EMI) filters, designed to maintain the accuracy of analog systems by reducing the effects of radio frequency (RF) interference. The LMV83x op amps are said to deliver an industry topping 120dB EMI rejection ratio, and feature 3 MHz unity gain bandwidth while operating on 240 uA of supply current.

The LMV831 single, LMV832 dual and LMV834 quad EMI-hardened op amps are suitable for use in phone accessories, medical instruments, precision weigh scales and other industrial electronic equipment that are sensitive to electromagnetic disturbances in noisy environments. Nat Semi gives an example application of an injected RF signal in a weigh scale, which can result in a 1V of output offset that would diminish a 10 bit analog-to-digital converter's resolution to the equivalent of only 3 bits. The company claims that an LMV83x op amp would only reduce resolution by 0.2 bits. Meanwhile, Nat Semi notes that a wide range of applications can benefit from EMI protection, including filters/buffers, photodiode preamp and piezoelectric sensors.

All three devices feature CMOS inputs, a maximum input offset voltage of 1 mV, a rail-to-rail output stage and an input common-mode voltage range that includes ground. These devices provide a common-mode rejection ratio (CMRR) and a power supply rejection ratio (PSRR) of 93 dB. The LMV83x devices maintain stability for capacitive loads up to 200 pF and offer a wide temperature range of -40 degrees C to 125 degrees C. The LMV831 comes in a 5-pin SC70 package, while the LMV832 is available in an 8-pin MSOP package and the LMV834 in a 14-pin TSSOP.

The LMV83x devices join the previously released LMV851/52/54 with 8 MHz unity gain bandwidth and LMV861/62 with 30 MHz of unity gain bandwidth. Built on National's CMOS7 process technology, which optimises performance as well as maximising power-efficiency, these op amps boast a power-to-performance ratio 80 uA per MHz, placing them in National's PowerWise family of energy-efficient products.

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