OPA607

OPA607

-20

-16

-12

-8

-4

0

4

8

12

16

20

-2

-0.5

-1.2

-0.4

-0.4

-0.3

0.4

-0.2

1.2

-0.1

2

0

2.8

0.1

3.6

0.2

4.4

0.3

5.2

0.4

6

0.5

D003

Measured Output

Ideal Output

% Error w/o offset correction

% Error with offset correction

17

OPAX607

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SBOS981B – OCTOBER 2019 – REVISED FEBRUARY 2020

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The target of the design is to achieve 0.1% measurement accuracy across –8 A to 12 A. As shown in Figure 10,

a DC accuracy of higher than 0.05% is achieved with the OPAX607. The simulations are captured with and

without voltage offset calibration. The error at the output of the OPAX607 increases drastically below –8 A and

with a suitable ADC enables a wider current measurement range to be obtained. Similarly reducing the gain from

9.2.2.3 Application Curves

Figure 9. OPA607 Settling Performance With the ADS7042

Figure 10. DC Current-Sense Transfer Function

9.2.3

Ultrasonic Flow Meters

Figure 11. High-Gain Ultrasonic Front-End

9.2.3.1 Design Requirements

The OPAX607 has a wide operating voltage range of 2.2 V to 5.5 V with a maximum quiescent current of 1 mA.

The availability of the inbuilt shutdown function enables designers to power cycle the front-end signal chain,

reducing the net quiescent current even further. The minimum operating voltage range of 2.2 V proves to be very

suitable for battery-powered applications such as the ultrasonic-based flow meters. The high-gain bandwidth of

the OPAX607 enables the gain stages and the ADC drive stages to be designed and combined, thereby

reducing component count. A schematic similar to that of Figure 7 can be used in ultrasonic flow meters for the

front-end signal chain.

The Ultrasonic sensing subsystem reference design for gas flow measurement design guide has a detailed

design procedure for ultrasonic-based sensing for gas flow measurement. The OPAX607 is a very suitable op

amp for the discrete front-end design described in this design guide.