AN3222

Theoretical and practical measurements

Doc ID 17551 Rev 1

9/18

Rs has been calculated for a maximum sense voltage of 50 mV (it represents 1% of the

voltage drop for a 5 V voltage source).

5.2

Practical results

This section summarizes the results of four practical measurements (Figure 6 to Figure 9).

●

Case 1: Rshunt = 3 m

Ω, Rg = 100 Ω, Rf = 150 kΩ, max = 1 A

●

Case 2: Rshunt = 10 m

Ω, Rg = 100 Ω, Rf = 47,5 kΩ, max = 1 A

●

Case 3: Rshunt = 30 m

Ω, Rg = 100 Ω, Rf = 16,2 kΩ, max = 1 A

●

Case 4: Rshunt = 100 m

Ω, Rg = 100 Ω, Rf = 4,75 kΩ, max = 1 A

For each condition, five TS507 operational amplifiers have been measured with the same

board. All resistors have an accuracy of 0.1% except for the shunt resistors, which have an

accuracy of 1%.

The left part of the figure shows the output voltage versus Isense/Imax. The maximum and

minimum theoretical output voltages are shown in red and blue respectively. These have

been calculated using Equation 3 on page 7. You can see that the output voltage of the

operational amplifiers is as predicted between these two trends.

The right part of the figure shows the absolute error on the output voltage versus

Isense/Imax. The red trend shows the maximum theoretical error that can occur. As

expected, all of our measurements are below this trend. The main error is due to Vio: the

lower Vio is, the more accurate the results will be.

Table 1.

Maximum error on measured value depending on Imax for TS507

Imax

Rs (

Ω)Rg (Ω)Rf (Ω)

Isense/Imax (%)

ε = 1%

ε = 0.1%

ε = 0.1%

1

3

10

30

100

1

0.05

100

9k76

21

7.6

3.1

1.7

1.4

2

0.02

100

12k1

25.5

9.3

3.6

2

1.4

3

0.01

100

16k2

32

12

4.3

2.3

1.5

4

0.01

100

12k1

25.2

9.2

3.5

2

1.5

5

0.01

100

9k76

22

8.1

3.3

1.9

1.4

7

0.005

100

14k

30.7

11

4.1

2.2

1.5

10

0.005

100

9k76

21.9

8.1

3.3

1.9

1.4

12

0.003

100

13k5

30

10.8

4.1

2.2

1.5

15

0.003

100

10k9

24.2

8.9

3.5

2

1.4

20

0.002

100

12k1

27

9.7

3.8

2.1

1.5

Max

| Error| (%)