Time(100 s/div)

m

+18V

-18V

37V

PP

SineWave

( 18.5V)

±

Device

V

IN

V

OUT

OPA188

www.ti.com

SBOS642A – MARCH 2013 – REVISED MARCH 2013

GENERAL LAYOUT GUIDELINES

For best operational performance of the device, good printed circuit board (PCB) layout practices are

recommended. Including:

•

Low-ESR, 0.1-µF ceramic bypass capacitors should be connected between each supply pin and ground,

placed as close to the device as possible. A single bypass capacitor from V+ to ground is applicable to

single-supply applications.

•

In order to reduce parasitic coupling, run the input traces as far away from the supply lines as possible.

•

A ground plane helps distribute heat and reduces EMI noise pickup.

•

Place the external components as close to the device as possible. This configuration prevents parasitic

errors (such as the Seebeck effect) from occurring.

•

Consider a driven, low-impedance guard ring around the critical traces. A guard ring can significantly

reduce leakage currents from nearby traces that are at different potentials.

PHASE-REVERSAL PROTECTION

The OPA188 has an internal phase-reversal protection. Many op amps exhibit a phase reversal when the input is

driven beyond its linear common-mode range. This condition is most often encountered in noninverting circuits

when the input is driven beyond the specified common-mode voltage range, causing the output to reverse into

the opposite rail. The OPA188 input prevents phase reversal with excessive common-mode voltage. Instead, the

output limits into the appropriate rail. This performance is shown in Figure 40.

Figure 40. No Phase Reversal

INPUT BIAS CURRENT CLOCK FEEDTHROUGH

Zero-drift amplifiers, such as the OPA188, use switching on their inputs to correct for the intrinsic offset and drift

of the amplifier. Charge injection from the integrated switches on the inputs can introduce very short transients in

the input bias current of the amplifier. The extremely short duration of these pulses prevents them from being

amplified, however they may be coupled to the output of the amplifier through the feedback network. The most

effective method to prevent transients in the input bias current from producing additional noise at the amplifier

output is to use a low-pass filter such as an RC network.

INTERNAL OFFSET CORRECTION

The OPA188 op amp uses an auto-calibration technique with a time-continuous 750-kHz op amp in the signal

path. This amplifier is zero-corrected every 3

μs using a proprietary technique. Upon power-up, the amplifier

requires approximately 100

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Product Folder Links: OPA188