OPAX607 datasheet(26/52 Pages) TI

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)

(I=T .) F

F 85

(I=T .)

(3)

Where,

• VIN(maximum) is the maximum input transient voltage seen by the circuit

• VD is the forward voltage drop of ESD diodes at the amplifier input

• ID(maximum) is the maximum current rating of the ESD diodes at the amplifier input

For a difference amplifier gain of 20 V/V, RF and RG of 12 kΩ and 600 Ω are used, respectively. With a

clock frequency of 40 MHz and ADS7056 sampling at 1 MSPS, the available acquisition time for amplifier

output settling is 550 ns. Figure 9-2 shows the simulation results for the circuit in Figure 9-1. The worst-case

peak-to-peak input transient condition is simulated. The output of the OPAx863 device settles to within 0.1%

accuracy within 543 ns. If using a slower clock frequency with the ADC is desired, then the acquisition time

reduces with the same sampling rate, which degrades measurement accuracy. Alternatively, the sampling rate

may be reduced to recover the required acquisition time and 0.1% accuracy.

9.2.3 Application Curves

Time (150 ns/div)

-2

-1.5

0.1

-1

0.2

-0.5

0.3

0.4

0.5

0.6

1.5

0.7

0.8

2.5

0.9

3.5

1.1

1.2

D805

VIN x 20

OPAx863 O/P

S/H Voltage

% Error

Figure 9-2. 0.1% Settling Performance

9.3 Front-End Gain and Filtering

RBIAS

-VBIAS

RISO

VS+

VS-

CSH

High-Gain Band Pass Filt er

High-Speed Peak Detector

Figure 9-3. High-Gain Narrow Bandpass Filter and Peak Detector Circuit

Ultrasonic signaling is used for proximity and obstacle detection, level sensing, sonars, and so forth. Such signal

chains detect the amplitude of received ultrasonic signal at a particular center frequency. Figure 9-3 shows a

high-gain narrow bandpass filter and peak detector circuit using any of the OPAx863 devices. The signal at the

frequency of interest is filtered out, gained, and peak detected to report the amplitude at the output of this circuit.

The phase information is lost in this circuit. The OPAx863 devices are used with its 50-MHz GBW to add a

single-stage gain and filtering, and the peak detection capability is easily made with the RRIO capability of these

amplifiers.

OPA863, OPA2863, OPA4863

SBOS982I – JUNE 2020 – REVISED DECEMBER 2022

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