AMP01EX datasheet(22/30 Pages) AD

22 / 30 page

Data Sheet

AMP01

Rev. E | Page 21 of 29

If heavy output currents are expected and the load is situated

some distance from the amplifier, voltage drops due to track or

wire resistance cause errors. Voltage drops are particularly

troublesome when driving 50 Ω loads. Under these conditions,

the sense and reference terminals can be used to remote sense

the load, as shown in Figure 36. This method of connection

puts the I × R drops inside the feedback loop and virtually

eliminates the error. An unbalance in the lead resistances from

the sense and reference pins does not degrade CMR, but does

change the output offset voltage. For example, a large unbalance

of 3 Ω changes the output offset by only 1 mV.

DRIVING 50 Ω LOADS

Output currents of 50 mA are guaranteed into loads of up to

50 Ω and 26 mA into 500 Ω. In addition, the output is stable

and free from oscillation even with a high load capacitance.

The combination of these unique features in an instrumentation

amplifier allows low level transducer signals to be conditioned

and directly transmitted through long cables in voltage or current

form. Increased output current brings increased internal

dissipation, especially with 50 Ω loads. For this reason, the

power-supply connections are split into two pairs; Pin 10 and

Pin 13 connect to the output stage only, and Pin 11 and Pin 12

provide power to the input and following stages. Dual supply

pins allow dropper resistors to be connected in series with the

output stage so excess power is dissipated outside the package.

Additional decoupling is necessary between Pin 10 and Pin 13

to ground to maintain stability when dropper resistors are used.

Figure 37 shows a complete circuit for driving 50 Ω loads.

AMP01

+IN

–IN

V–

V+

SENSE

REFERENCE

OUTPUT

GROUND

TWISTED

PAIRS

REMOTE

LOAD

IN4148 DIODES ARE OPTIONAL. DIODES LIMIT THE OUTPUT

VOLTAGE EXCURSION IF SENSE AND/OR REFERENCE LINES

BECOME DISCONNECTED FROM THE LOAD.

Figure 36. Remote Load Sensing

+IN

–IN

AMP01

5kΩ

130Ω

0.047µF

+15V

SENSE

REFERENCE

VOUT

±3V MAX

50Ω

LOAD

0.047µF

130Ω

0.047µF

–15V

POWER BANDWIDTH, G = 100, 130kHz

POWER BANDWIDTH, G = 10, 200kHz

THD: ~0.04% AT 1kHz, 2V rms

VOLTAGE GAIN, G =

R1 AND R2 RESISTORS REDUCE IC DISSIPATION

Figure 37. Driving 50 Ω Loads

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