LTC6373

19

Rev. 0

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APPLICATIONS INFORMATION

Keep in mind that any change in voltages applied to A2 or

A1 or A0 pins from logic low to logic high (or vice versa)

immediately results in a gain setting change for LTC6373

(transparent mode).

Valid Input and Output Range

Instrumentation amplifiers traditionally specify a valid

input common mode range and an output swing range.

This however often fails to identify swing limitations

associated with internal nodes, as they experience a combi-

nation of gained differential signal and common mode sig-

nal. Referring to the Simplified Block Diagram of Figure 1,

the output swing of amplifiers A1, A2, and A3 as well as

the common mode input range of the output differential

amplifier A3 impose limitations on the valid operating

range. The graphs in Figure 2 show the maximum input

common mode voltage limits where a valid output is pro-

duced for each gain setting of LTC6373.

Figure 2. Input Common Mode Range vs Differential Output Voltage for Each Gain Setting of LTC6373 with No Load

6373 F02

+

–

LTC6373

+OUT

–OUT

+–

+

–

+–

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02a

G = 16

(a)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02b

G = 8

(b)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02c

G = 4

(c)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02d

G = 2

(d)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02e

G = 1

(e)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02f

G = 0.5

(f)

DIFFERENTIAL OUTPUT VOLTAGE (V)

–30 –24 –18 –12 –6 0

6 12 18 24 30

–15

–12

–9

–6

–3

0

3

6

9

12

15

6373 F02g

(g)

G = 0.25