INDUSTRIAL VOLTAGE AMPLIFIER IC

AM401

analog microelectronics

Mars 2006

Analog Microelectronics GmbH

Phone:

+49 (0)6131/91 073 – 0

12/21

An der Fahrt 13, D – 55124 Mainz

Fax:

+49 (0)6131/91 073 – 30

Rev. 2.3

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

Application 2 – Voltage output signal of 0...5/10V, current-driven sensing element

In this application the additional OP is used as a current source for a resistor measuring bridge. The

values of the external components have been calculated for an output voltage of 0...5V; the pin used

to configure the instrumentation amplifier offset (ZA) is connected to the IC’s Ground. Gain G is

set using the two external resistors R1 and R2:

()

2

1

1

R

R

G

G

G

G

IA

OP

IA

+

=

=

(2)

If no offset voltage is present, the transfer function of the output voltage (Gl.1) is:

VOUT = G VIN

(1)

Using these equations the values of resistors R1 and R2 can be set as follows:

1

2

1

−

=

IN

IA

OUT

V

G

V

R

R

Supply current IS for the sensor bridge can be determined using resistance RSET:

I

V

R

S

BG

SET

=

(8)

C

2

C

1

R

2

R

1

R

REF

R

SET

Ground

V

OUT

V

CC

V

IN

1

2

3

4

14

13

5

6

11

15

12

V

BG

CVREF

CVSET

IN+

IN_

GND

ZA

OUTIA

INOP

7

8

GAIN

VOUT

VCC

VREF

VSET

Voltage Reference

AM401

+

_

OP2

+

_OP1

+

_ IA

Figure 4:

Application for current-driven sensing elements