INDUSTRIAL VOLTAGE AMPLIFIER IC

AM401

analog microelectronics

Mars 2006

Analog Microelectronics GmbH

Phone:

+49 (0)6131/91 073 – 0

7/21

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

DETAILED DESCRIPTION OF FUNCTIONS

AM401 is a monolithically integrated voltage transmitter which has been designed for the

conditioning of differential bridge voltages and for the conversion of voltage signals referenced to

ground. By varying just a few external components the output voltage can be adjusted over a wide

range. All of the function blocks are individually accessible, enabling them to be used as functional

units or, using the relevant external circuitry, configured as an application-specific device. Typical

applications and values for external components are given in the examples described in the

following.

In essence AM401 consists of 4 functional blocks as shown in Figure 1. The individual blocks are

as follows:

1. The core element of AM401 is its high-precision instrumentation amplifier (IA) with an internal

gain of GIA and the ability to set the reference potential of the amplifier externally (pin ZA). The

IA acts as an input stage for differential voltage signals.

2. There is also an operational amplifier stage (OP1). OP1’s gain of GOP1 can be set using external

resistors R1 and R2 (see Figure 2). The operational amplifier output has been designed in such a

way that with certain loads it can be set down to zero. In addition, the output stage can drive up

to a maximum of 10mA without an external transistor having to be connected. An output current

limit has been implemented as a protective feature which guards the IC at the output in the event

of a short-circuit.

3. AM401’s voltage reference permits voltage to be supplied by external components (such as

sensors, microprocessors, etc.). The reference voltage VREF has a value of either 5V or 10V.

External capacitance C1 acts as a reference voltage stabilizer. It must also be connected when

the voltage reference is not in use (see: Figure 2).

4. An additional operational amplifier (OP2) can be used as a current or voltage source for the

supply of external components. OP2’s positive input is connected internally to voltage VBG so

that the output current or voltage can be set across a wide range using one or two external

resistors. Descriptions of the relevant applications can be found on the following pages. The

operational amplifier output has a sufficiently high drive power.

One of AM401’s main features is its range of integrated protective circuits which make the IC an

effective output stage.

• Pins VOUT, VCC and GND are protected against reverse polarity across the entire supply

voltage range without the need for any additional external components.

• The output of the IC is protected against short-circuiting.

• All pins (with the exception of VOUT, VCC and GND) are protected by internal ESD diodes.