8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

The OPAx863A are classic voltage-feedback amplifiers, where each channel has two high-impedance inputs and

a low-impedance output. Theses devices feature a GBW of 50 MHz, 6.3

‑nV/√Hz noise, RRIO capability, and

high-precision performance consuming only 800 µA of quiescent current. These features make the OPAx863A

an excellent choice for use in precision data acquisition, reference buffering with fast settling, high gain, and

filter circuits. The overload power limit feature makes the OPAx863A truly low power in high-gain multichannel

systems, and limits any increase in quiescent current during output overload conditions.

8.2 Typical Applications

8.2.1 Active Filters

Active filter circuits are used to amplify signals in the pass band, attenuate signals in the stop band, and also

limit the integrated noise at the amplifier output. The OPAx863A, with a wide bandwidth and high-precision

performance, is an excellent device for designing multifeedback (MFB) low-pass filter circuits.

8.2.1.1 Design Requirements

This section discusses the design of a MFB low-pass active filter with a cut-off frequency at 2 MHz and the

impact of amplifier gain-bandwidth (GBW) on filter performance.

8.2.1.2 Detailed Design Procedure

Figure 8-1 shows the use of OPAx863A in a second-order multifeedback (MFB) low-pass filter with a cut-off

frequency of 2 MHz. The frequency response of the circuit in Figure 8-1 is compared for various amplifiers with

different gain-bandwidth products and shown in Figure 8-2:

+

–

1k

1k

VS+

VS-

37pF

1k

+

–

VIN

VOUT

OPAx863A

168pF

Figure 8-1. MFB Low-Pass Filter Circuit Using the OPAx863A

Table 8-1. Impact of Amplifier GBW on Cutoff Frequency

DEVICE

GBW (MHz)

CUTOFF FREQUENCY (MHz)

TLV9051

5

1.59

LMV641

10

1.78

OPA2834

20

1.87

OPAx863A

50

1.95

OPA836

110

1.98

OPA863A, OPA2863A

SBOSA95D – MAY 2022 – REVISED DECEMBER 2023

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