Precision amplifier for bridge circuits

AM467

analog microelectronics

February 2007

Analog Microelectronics GmbH

Phone: +49 (0)6131/91 073 – 0

5/9

An der Fahrt 13, D – 55124 Mainz

Fax:

+49 (0)6131/91 073 – 30

Rev. 1.0

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

EXTERNAL COMPONENTS

Parameter

Symbol

Conditions

Min.

Typ.

Max.

Unit

Output Capacitor

1

5

nF

Compensation Capacitor

100

pF

Stabilization Capacitor (optional)

100

nF

EMV Protection Capacitor (optional)

470

pF

Vout = max. Vout

20

k

Ω

Table 2: External components of the calibration network

Recommended: ceramic capacitors

DESCRIPTION OF FUNCTIONS

AM457 is an integrated precision circuit for the signal amplification of high-impedance signal

sources and for the signal conditioning of sensor bridges with low sensitivity, particularly for

ceramic and DMS sensing elements or GMR measuring cells.

The IC generates a rail-to-rail output signal of 0.2 V to Vcc-0.2 V. The amplification and offset can

be set independently of one another using external resistors. Through the suitable dimensioning of

external resistors in particular an output voltage of 0.5...4.5 V can also be provided. As these values

are standard the following description refers to this output voltage.

AM467 works on the principle of ratiometry with a supply voltage of 5 V ±5%. The IC is

distinguished by its low offset and extremely low thermal offset drift across a wide temperature

range, enabling it to be classified as a precision amplifier.

The sink and source output stage is protected internally against short-circuiting.

The AM467 design incorporates protective measures against interference from EMV and ESD

using suitable semiconductor structures.

With the exception of the additional operational amplifier and the diagnostic unit the IC is

compatible with AM457. AM467 thus has a smaller chip surface and a lower power consumption.

AM467 can be used as an autonomous signal conditioning IC or as a preamplifier for an A/D

converter for back-end digitization.

EXAMPLE APPLICATION

AM457 is suitable for the amplification of resistance networks connected up as a Wheatstone

bridge with four resistors and which have a low sensitivity, such as 1.0 to 3.5 mV/V with a 5 V

supply, for example. By way of example a sensor application is described herein which is