AM400 datasheet(9/21 Pages) AD

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UNIVERSAL AMPLIFIER IC

AM400

analog microelectronics

October 2005

Analog Microelectronics GmbH

Phone:

+49 (0)6131/91 073 – 0

9/21

An der Fahrt 13, D – 55124 Mainz

Fax:

+49 (0)6131/91 073 – 30

Rev.: 4.2

Internet: http://www.analogmicro.de

Email:

info@analogmicro.de

4. The voltage-to-current converter (V/I converter) provides a voltage-controlled current signal at

IC output IOUT which activates an external transistor T1; this reduces the power dissipation of

the IC and supplies the output current IOUT. The external transistor is protected against reverse

polarity by an additional diode D1. Via pin SET an offset current ISET can be set at output IOUT

(with the help of the internal voltage reference and an external voltage divider as shown in

Figure 5, for example). External resistor R0 permits the output current to be finely adjusted with

parallel operation of current and the voltage output. For the output current IOUT boosted by T1

the following ratio applies:

SET

INDAI

OUT

with

SET

SET =

(4)

with VINDAI the voltage at pin INDAI and VSET the voltage at pin SET (V/I converter inputs, see

Figure1)2.

5. The AM400 reference voltage source enables voltage to be supplied to external components

(such as sensors, microprocessors, etc.). The reference voltage value VREF can be set via pin

VSET. If pin VSET is not connected, VREF = 5V; if VSET is switched to ground, VREF = 10V.

Values between the above can be set if two external resistors are used (inserted between pin

VREF and pin VSET and between pin VSET and GND).

External capacitor C1 stabilizes the reference voltage. It must be connected even if the voltage

reference is not in use. It also must not exceed the minimum value.

6. The additional operational amplifier (OP3) can be used as a current or voltage source for the

supply of external components. OP3’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.

2 The construction of the V/I converter is such that output current IOUT is largely independent of the current

amplification

βF of external transistor T1. Production-specific variations in the current amplification of the transistors

used are compensated for internally by the V/I converter.

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