TL032AIDE4 datasheet(45/68 Pages) TI

45 / 68 page

TL03x, TL03xA

ENHANCED-JFET LOW-POWER LOW-OFFSET

OPERATIONAL AMPLIFIERS

SLOS180C – FEBRUARY 1997 – REVISED DECEMBER 2001

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

4-mA to 20-mA current loops

Often, information from an analog sensor must be sent over a distance to the receiving circuitry. For many

applications, the most feasible method involves converting voltage information to a current before transmission.

The following circuits give two variations of low-power current loops. The circuit in Figure 66 requires three wires

from the transmitting to receiving circuitry, while the second variation in Figure 67 requires only two wires, but

includes an extra integrated circuit. Both circuits benefit from the high input impedance of the TL03xA because

many inexpensive sensors do not have low output impedance.

Assuming that the voltage at the noninverting input of the TL03xA is zero, the following equation determines

the output current:

O +

) 5V

+ 0.16

I )

4mA

The circuits presently provide 4-mA to 20-mA output current for an input voltage of 0 to 100 mV. By modifying

R1, R2, and R3, the input voltage range or the output current range can be adjusted.

Including the offset voltage of the operational amplifier in the above equation clearly illustrates why the low offset

TL03xA was chosen:

O +

) 5V

)

) R1

+ 0.16

I )

4mA – 0.17

For example, an offset voltage of 1 mV decreases the output current by 0.17 mA.

Due to the low power consumption of the TL03xA, both circuits have at least 2 mA available to drive the actual

sensor from the 5-V reference node.

TL032AIDE4 Datasheet(PDF) 45 Page - Texas Instruments