CMOS op amp eliminates oscillation, says Rohm

Equipped with anomaly detection, the BD77501G is the latest high speed CMOS operational amplifier released by Rohm Semiconductor. The op amp has been added to the company’s high noise immunity Emarmour series.

The high speed, ground sense CMOS op amp is optimised for industrial and consumer equipment requiring high-speed sensing, explains Rohm. For example it can be used in anomaly detection systems used in measurement and control equipment and sensors that work with very small signals.

Op amps are used in automotive and industrial applications to quickly amplify minute sensor signals in anomaly detection systems that provide safety. They are susceptible to oscillation due to capacitive loads (i.e. from wiring), making board design challenging. At the same time, degradation of the noise environment resulting from increased electrification and mounting density makes it difficult to implement noise design for small-signal devices.

Rohm’s Emarmour series of op amps and comparators are specified for automotive and industrial markets due to its superior noise immunity that allows users to reduce design resources to address noise issues. According to Rohm, the BD77501G is the industry’s first op amp that not only supports high-speed amplification (high slew rate: 10V/microsecond) and eliminates oscillation caused by load capacitance. Conventional high speed op amps can become unstable due to load-capacitance-induced oscillation. The output voltage for conventional products can fluctuate by ±200mV or more across the entire noise frequency band but the BD77501G provides unprecedented electromagnetic immunity (EMI) that limits variation to less than ±20mV (1/10th). This enables high-speed signal amplification without being affected by load capacitance or external noise when installed in the latter stages of sensor applications, explains Rohm, to improve reliability and reduce design time.

The BD77501G uses Rohm’s proprietary Nano Cap power supply technology to achieve stable control.

It provides superior noise immunity that eliminates the need for external noise countermeasure components conventionally required for standard products (i.e. RC filters for the power supply, input, and output pins).

The BD77501G is sampling now, with OEM quantities scheduled for October 2020.

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