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CMOS op amp has low noise for high accuracy

The device can be used in applications that demand high-accuracy sensing, including sonar and optical sensors that handle ultra-small signals. Other suitable applications are security systems, IR remote controls, night vision, and other sets equipped with IR sensors, devices demanding high accuracy operation (i.e. HDD), equipment management systems including flow meters and gas detectors and any other industrial and consumer sets integrating sensors requiring high accuracy detection.

The advance of the IoT has led to sensors being adopted in a variety of applications from portables and vehicle systems to industrial equipment, where they are used to detect and convert various environmental and physical changes into signals, sensors demand high accuracy. At the same time, however, peripheral sensor circuitry is moving towards lower voltages to achieve greater power savings.

The LMR1802G-LB was developed using the company’s analogue technology covering circuit design, processes, and layout. It reduces input equivalent noise voltage density by half (2.9nV/√Hz at 1kHz, 7.8nV/√Hz at 10Hz) compared to conventional products, says the company, to improve the detection performance of sensor signals. Phase margin of 68, claimed to be the best in class, and capacitive load tolerance of 500pF provide stability for the accurate amplification of voltages in the order of µV, to support applications requiring high-precision sensing.

The op amp minimises input offset voltage and input bias current. In op amp configuration, the output voltage should be 0V when the input is 0V, but an offset voltage is often generated as an error. If the sensor’s output impedance is high, the sensor output voltage will be affected if the input bias current of the op amp is large.

These two error factors must be made as small as possible to ensure optimal performance. The op amp offers an input offset voltage of 450µV and input bias current of only 0.5pA; four and two times less than conventional products, respectively, says the company, for accurate amplification.

The op amp is sampling now, with OEM quantities scheduled for October 2018.


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