5962-88630023A データシートの表示（PDF） - Analog Devices

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5962-88630023A

Low Noise, Precision Instrumentation Amplifier

Analog Devices 

AMP01

If heavy output currents are expected and the load is situated

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

wire resistance will 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 33. 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 will change the

output offset voltage. For example, a large unbalance of 3 Ω will

change the output offset by only 1 mV.

DRIVING 50 ⍀ 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 cur-

rent 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; pins 10 and

13 connect to the output stage only and pins 11 and 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 pins 10 and 13 to ground to

maintain stability when dropper resistors are used. Figure 34

shows a complete circuit for driving 50 Ω loads.

V+

RS

14

*IN4148 DIODES ARE OPTIONAL. DIODES LIMIT THE OUTPUT

VOLTAGE EXCURSION IF SENSE AND/OR REFERENCE LINES

BECOME DISCONNECTED FROM THE LOAD.

+IN

18

15

SENSE

12

1

13

7

*

RG

AMP01

9

8

2

10

REFERENCE

TWISTED

PAIRS

–IN

3

11

*

OUTPUT

GROUND

V–

Figure 33. Remote Load Sensing

REMOTE

LOAD

POWER BANDWIDTH, G = 100, 130kHz

POWER BANDWIDTH, G = 10, 200kHz

T.H.D.~0.04% @ 1kHz, 2Vrms

18

+IN

1

RG

2

RS

5k⍀

R1

130⍀

1W

14

15

C1

0.047␮F

12

AMP01

SENSE

13

7

9

8

10 REFERENCE

0.047␮F

–IN

3

11

C2

0.047␮F

( ) 20 ؋ RS

VOLTAGE GAIN, G =

RG

RESISTERS R1 AND R2 REDUCE IC DISSIPATION

R2

130⍀

1W

Figure 34. Driving 50 Ω Loads

0.047␮F

+15V

VOUT

؎3V MAX

50⍀

LOAD

–15V

–14–

REV. D

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