AN2648

STLM20 temperature-to-output transfer function

7/15

Equation 2 is the basic difference amplifier equation.

Equation 2

If R1 = R2 and R3 = R4, then it reduces to:

However, obtaining perfectly identical resistors is nearly impossible. Thus, the more

complex expression of Equation 2 is used. Starting with Equation 1 on page 2, for Figure 6,

we have:

R1

R3

V

R1

R2)

(R4

R4

R1)

R3

(

V2

V

1

OUT

⋅

−

+

+

=

1

3

1

2

OUT

R

R

)

V

V

(

V

−

=

V

1.8663

+

T

0.01169

V

O

⋅

−

=

R1

R3

V

R1

R2)

(R4

R4

R1)

R3

(

V2

V

O

OUT

⋅

−

+

+

=

R1

R3

1.8663)

+

T

0.01169

(

R1

R2)

(R4

R4

R1)

R3

(

V2

V

OUT

⋅

⋅

−

−

+

+

⋅

=

R1

R3

1.8663

T

R1

R3

0.01169

R1

R2)

(R4

R4

R1)

R3

(

V2

V

OUT

⋅

−

⋅

⋅

+

+

+

⋅

=