OA1ZHA datasheet(22/35 Pages) STMICROELECTRONICS

22 / 35 page

Application information

OA1ZHA, OA2ZHA, OA4ZHA

22/35

DocID025994 Rev 2

5.9

Optimized application recommendation

OA1ZHA, OA2ZHA and OA4ZHA CMOS op amp are based on chopper architecture. As

they are switched devices, it is strongly recommended to place a 0.1 µF capacitor as close

as possible to the supply pins.

A good decoupling has several advantages for an application. First, it helps to reduce

electromagnetic interference. Due to the modulation of the chopper, the decoupling

capacitance also helps to reject the small ripple that may appear on the output.

OA1ZHA, OA2ZHA and OA4ZHA CMOS op amp have been optimized for use with 10 kΩ

in the feedback loop. With this, or a higher value of resistance, these devices offer the best

performance.

5.10

EMI rejection ration (EMIRR)

The electromagnetic interference (EMI) rejection ratio, or EMIRR, describes the EMI

immunity of operational amplifiers. An adverse effect that is common to many op amp is a

change in the offset voltage as a result of RF signal rectification.

OA1ZHA, OA2ZHA and OA4ZHA CMOS op amp have been specially designed to minimize

susceptibility to EMIRR and show an extremely good sensitivity. Figure 46: "EMIRR on IN+

pin" shows the EMIRR IN+ of the OA1ZHA, OA2ZHA and OA4ZHA measured from 10 MHz

up to 2.4 GHz.

Figure 46: EMIRR on IN+ pin

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