Noise Characteristics (EMI/EMS)

The trend towards greater electronification and application density is causing the noise environment to worsen, making noise suppression a major issue for op amps that amplify small signals (i.e. from sensors).
In recent years, the lineup of op amps strong against noise has been increasing to meet this growing demand. This section will provide a definition of noise.

Definition of Noise

Noise is commonly called EMC (Electromagnetic Compatibility), which indicates the ability to not interfere with other devices due to noise while also maintaining performance even when subjected to noise interference from other devices. However, when used in certain fields it is divided into two categories, EMI and EMS.

Definition of Noise

EMI Electromagnetic Interference

EMI is used as an indicator for how much noise is generated when operating the target product, which may cause problems in surrounding ICs and systems. ‘Good’ EMI characteristics mean less noise is generated.
Op amp noise, referred to as equivalent noise voltage, is generated from circuits and processes. This noise becomes an error voltage during signal amplification and can affect amplification accuracy.

Effects of Op-Amp-Generated Noise: Image

ROHM offers a broad lineup of low-noise op amps. Please refer to the product page for details.

 > High-Performance CMOS Ground Sense Low Noise Op Amps (Product Search)

 > Low Noise Op Amps (Product Search)

EMS Electromagnetic Susceptibility

Disturbance noise can cause IC or set malfunction.
EMS is an indicator of a device’s ability to resist malfunction when subjected to disturbance noise. Therefore, ‘Good’ EMS characteristics mean that the product is less susceptible to the effects of noise.
In the op amp sector, ‘Good EMS characteristics which is less susceptible to noise’ is expresses as ‘High EMI immunity’ to indicate high immunity to electromagnetic interference from external noise.

‘Good EMS Characteristics’ = ‘High EMI Immunity’

In other words, a high EMI immunity op amp means that the op amp is not susceptible to external noise.

Effects of Disturbance Noise: Image

ROHM offers a broad lineup of high EMI immunity op amps. Please refer to the product page for details.

 > High EMI Immunity Ground Sense Op Amps (Product Search)

 > High EMI Immunity Rail-to-Rail Op Amps (Product Search)

The next page describes the typical parameters of op amps, such as amplification factor and voltage gain.