AM417 – Ratiometric instrumentation

amplifier with adjustable output stage

Analog Microelectronics GmbH

An der Fahrt 13, D – 55124 Mainz

July 2008 –Rev 3.1- Page 12/18

Phone:+49 (0)6131/91 073-0

Fax: +49 (0)6131/91 073-30

Email: info@analogmicro.de

and from Equation 11 we are presented with:

mV

mV

mV

V

V

RO

23

6

2

67

.

6

10

5

.

0

2

=













+

−

⋅

⋅

=

Referring to Equation 12 the resistance for offset calibration is thus:

Ω

=

⋅

=

46

2

0

0

IB

R

I

V

R

If

output signal offset of the overall circuit is set to

Example 3: Piezoresistive pressure sensing element in a bridge circuit with a high positive

offset

The sensing element is supplied with constant current. Taking the maximum output voltage of the

OP into account

The bridge voltage is:

V

k

mA

R

I

V

BR

BR

BR

3

3

1

'

=

Ω

⋅

=

⋅

=

.

The output voltage of the sensing element is corrected by the ratio of the bridge voltages:

mV

V

V

mV

V

OUTME

60

5

3

100

'

=

⋅

=

The offset voltage of the sensing element is also corrected by the ratio of the bridge voltages:

mV

V

V

mV

V

OSME

6

5

3

10

'

=

⋅

=

Applying Equation 5 the following is accrued:

67

.

6

10

60

4

=

⋅

=

mV

V

G

OUT