AM411

Low-Cost Voltage Transmitter IC

March 2015 - Rev. 4.0

Page 8/10

www.analogmicro.de

Example 1: Desired output voltage range 0 .. 5 V, input voltage range 0 .. 200 mV

In the following example a differential input voltage range of VIN = 0 .. 200 mV has to be amplified to an out-

put voltage range of 0 .. 5 V. Because of the desired maximum output voltage VOUT,max = 5 V a minimum

supply voltage of VCC,min = 10 V is needed. The dimensioning of the resistors R1 and R2 can be done using

equation (3).

With VIN,min = 0 V, VIN,max = 200 mV, VOUT,min = 0 V and VOUT,max = 5 V the following relation can be obtained

from equation (3):

2

1

4 R

R

⋅

=

Together with the boundary conditions given in Table 2 the following dimensioning of the external compo-

nents can be obtained:

R1 = 100 kΩ

R2 = 25 kΩ

C1 = 2.2 µF

Example 2: Desired output voltage range 1 .. 5 V, input voltage range 0 .. 160 mV

The circuit shown in Figure 3 can be used, if the system’s offset and gain have to be adjusted. To generate

VZA AM411’s voltage reference is used in combination with a voltage divider consisting of R3 and R4.

Using equation (3) as well as VIN,min = 0 V, VIN,max = 160 mV, VOUT,min = 1 V and VOUT,max = 5 V the following

relation can be obtained for R1 and R2:

2

1

4 R

R

⋅

=

and with equation (4) the voltage at pin ZA can be calculated to VZA = 200 mV.

Since VZA is adjusted using R3 and R4 and VREF = 5 V the following relation can be obtained:

1

5

4

3

−

=

ZA

V

V

R

R

(5)

With VZA = 200 mV this leads to R3 = 24 · R4.

Figure 3: AM411's external circuit for offset and gain adjustment