Precision amplifier for bridge circuits

AM467

analog microelectronics

February 2011

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. 1.1

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

EXTERNAL COMPONENTS

Parameter

Symbol

Conditions

Min.

Typ.

Max.

Unit

Output Capacitor

C1

1

5

nF

Compensation Capacitor

C2

80

100

120

pF

Stabilization Capacitor (optional)

C3

100

nF

EMV Protection Capacitor (optional)

C4

470

pF

Load Resistor to GND, to VCC

RL

Vout = max. Vout

20

k

Ω

Table 2: External components of the calibration network (see figure 2)

Recommended: ceramic capacitors

DESCRIPTION OF FUNCTIONS

AM467 is an integrated precision circuit for the signal amplification of high- and medium

impedance signal sources and for the signal conditioning of sensor (resistor) bridges with low

sensitivity, particularly for ceramic and DMS sensing elements or GMR measuring cells.

The IC is able to generates a rail-to-rail output signal of 0.2 V to Vcc-0.2 V. The output signal is

adjustable in offset and span. 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.

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

converter for digital signal conditioning. For higher output voltages e.g. 10Volt or 2(3)-wire current

output, this IC can be combined with the analog interface circuits of Analog Microelectronics (e.g.

AM461 and AM460)

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