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PDF AM447 Data sheet ( Hoja de datos )
| Número de pieza | AM447 | |
| Descripción | High Precision Instrumentation Amplifier | |
| Fabricantes | ETC | |
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High Precision Instrumentation Amplifier
AM447
FEATURES
• Very Low Offset Voltage: < 25µV
• Low Input Bias Current: ≤ 5nA
• High Input Sensitivity
• High CMRR: > 90dB min
• Wide Operating Temperature Range:
–40°C...+140°C
• Adjustable Rail–to–Rail Voltage Out-
put Stage: 0.5...4.5V
• Single Supply Device (ratiometric)
• Integrated Source and Sink Capabil-
ity: ±2mA
• Low Noise Behaviour
APPLICATIONS
• Small Signal (Bridge) Amplifier
Low Pressure Sensors
Automotive Applications
DMS Interface
Interface for Ceramic Sensors
• High Precision Amplifier
Medical Instrumentation
Data Acquisition
GENERAL DESCRIPTION
The AM447 is a high precision amplifier, de-
signed for amplification of sensor bridge sig-
nals up to 35mV full scale. The single supply
circuit consists of a high precision instrumen-
tation amplifier (IA) and an integrated ra-
tiometric output stage. Input offset voltages
less than ±25µV (±1µV/°C) are adjustable by
only two externally trimmable resistors. The
monitoring of the amplified signal is possible
at the output of the IA and makes the adjust-
ment easier. With the externally adjustable
gain of the output stage, the AM447 can be
used for different signal sources. The 2mA
sink and source capability makes it ideal for
high precision applications specially in the
field of automotive sensors.
DELIVERY
• DIL16 packages (samples, small quantities)
• SO16(n) packages
• Dice on 5“ blue foil
BLOCK DIAGRAM
OC1
1
AM447
OC2
2
VCC
14
IN+
4
IN-
3
IA
Output
Stage
1k 19k VCC
OUT
10
GAIN
11
58
6
12
97
RSET VREFIN VREF IAOUT VSET GND
Figure 1
analog microelectronics
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Internet: www.analogmicro.de
Phone: +49 (0)6131/91 073 – 0
Fax: +49 (0)6131/91 073 – 30
E–Mail: info@analogmicro.de
DataSheet4 U .com
April 2000
1/6
Rev. 2.1
1 page  
www.DataSheet4U.com
High Precision Instrumentation Amplifier
AM447
FUNCTIONAL DESCRIPTION
The IC AM447 is an integrated high precision amplifier for low bridge output signals. Basically the
AM447 is composed of 2 functional sections as shown in Figure 1:
1. A high accuracy instrumentation amplifier (IA) allows amplification with a high signal-to-noise
ratio. The two offset compensation resistors ROC1 and ROC2 offer the possibility to make the input
offset voltage of the instrumentation amplifier to nearly zero. But offset compensation over tem-
perature is only given if the resistors ROC1 and ROC2 have the same temperature coefficients. Fur-
thermore, these resistors have to be placed together very close. It is also necessary to use similar
metals for the connection of the sensor bridge and the AM447 to avoid thermocouple effects. The
internal gain of the IA is fixed to the value GINT = 102 . The output voltage VIAOUT (pin 10) of the
IA is given by the following equation:
( )VIAOUT = GINT ⋅ VIN + − VIN − + VVREF
2. An output stage de–couples the IA and thus improves the performance of the AM447. The gain
factor G is fixed by the two external resistors RG1 and RG2. The gain factor of the output stage is
defined by
G ADJ
= 1+
RG2
RG1
The output signal VOUT (pin 10) can be calculated with
( ) ( )VOUT = G VIN+ − VIN− + VVREF = G1IN4T 4⋅ G4A4DJ2V4IN+4−4VI4N3− +
V{VREF
Span adjustment
Offset adjustment for
kalibrated transducers
The AM447 is suited for two types of transducers. The IC is designed for usage with non-
compensated and non-calibrated sensors using resistors R1 and R2 for offset calibration as well as
for sensor systems with calibrated transducers. The remaining offset of the transducers can be cali-
brated by variation of VVREF. The adjustment of the offset is then:
VVREF
=
RO 2
RO1 + RO2
VCC
The entire sensor systems realised with the different types of AM447 and only a few external com-
ponents are shown in Figures 2 and 3.
Offset calibration of the instrumentation amplifier
The offset compensation has to be handled with care because the entire system performance de-
pends on it. Please note, that this offset adjustment doesn't include the bridge offset.
The offset compensation has to be done in the following order:
• T = 25° C and VCC = 5V
• VIN + = VIN − = VREF = 2.5V
• The voltage between VIAOUT (pin 12) and VREF (pin 6) has to be adjusted to zero Volt.
• VIAOUT is increased by increasing ROC1 and is decreased by increasing ROC2.
analog microelectronics
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April 2000
5/6
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| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet AM447.PDF ] | |
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