UNIVERSAL AMPLIFIER IC

AM400

analog microelectronics

October 2005

Analog Microelectronics GmbH

Phone:

+49 (0)6131/91 073 – 0

14/21

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

According to Equation 4 the following is then relevant to output current IOUT:

SET

I

IN

OUT

I

R

G

V

I

+

=

0

8

with

0

=

ZA

V

(15)

with













+

=

=

2

1

1

5

R

R

G

G

G

GAIN

IA

I

and

4

3

4

0

2

R

R

R

R

V

I

REF

SET

+

⋅

=

.

Example 1: VIN = 0...100mV (differential), IOUT = 4...20mA and VOUT = 0...10V

For a measuring bridge with a signal of VIN = 0...100mV at the IA input the external components are

to be dimensioned in such a way that the output current has a range of 4...20mA and the output

voltage one of 0...10V.

R1 and R2 are dimensioned in accordance with Equation 14, R0 according to Equation 4 and R3 and

R4 according to Equation 8. Observing the boundary conditions for the external components the

following values are then obtained:

R0 ≈ 35.5Ω

R1 ≈ 80.9kΩ

R2 = 10kΩ

R3 = 83kΩ

R4 = 5kΩ

R5 = 39Ω

RL = 0...600Ω

RIAL ≤ 10kΩ

C1 = 2.2µF

2) Typical 3-wire application with an input signal referenced to ground

Ground

V

S

I

OUT

V

OUT

R

1

R

2

R

3

R

4

C

1

R

0

T

1

D

1

R

5

R

L

1

V

IN

Input voltage

referenced to ground

Connections setting unused function blocks to a defined operating point

3-wire connection

V

BG

17

5

IA

7

6

10

18

15

14

13

12

11

20

V

I

16

19

Voltage reference

1

9

OP1

8

3

4

2

AM400-0

OP2

OP3

Figure 6:

Typical application for input signals referenced to ground