REV. A

OP471

–11–

High-Speed Differential Line Driver

The circuit of Figure 15 is a unique line driver widely used in

professional audio applications. With

±18 V supplies, the line

driver can deliver a differential signal of 30 V p-p into a 1.5 k

W

load. The output of the differential line driver looks exactly like

a transformer. Either output can be shorted to ground without

changing the circuit gain of 5, so the amplifier can easily be set

for inverting, noninverting, or differential operation. The line

driver can drive unbalanced loads, like a true transformer.

R2

5k

1/4

OP471E

+15V

–15V

R3

200

R1

50

R5

5k

1/4

OP471E

R6

200

R4

50

R8

5k

1/4

OP471E

R9

200

R7

50

R11

5k

1/4

OP471E

R12

200

R10

50

Figure 13. Low-Noise Amplifier

High-Output Amplifier

The amplifier shown in Figure 16 is capable of driving 20 V p-p

into a floating 400

W load. Design of the amplifier is based on a

bridge configuration. A1 amplifies the input signal and drives

the load with the help of A2. Amplifier A3 is a unity-gain inverter

which drives the load with help from A4. Gain of the high output

amplifier with the component values shown is 10, but can

easily be changed by varying R1 or R2.

10

0%

100

90

Figure 14. Noise Density of Low-Noise Amplifier, G = 100

R4

10k

1/4

OP471

R8

10k

R7

2k

R6

2k

R9

10k

1/4

OP471

R10

50

R2

2k

R3

2k

R5

10k

R14

1k

R12

1k

R13

10k

–OUT

+OUT

1/4

OP471

R1

10k

IN

R11

50

Figure 15. High-Speed Differential Line Driver

1/4

OP471E

A1

R1

1k

C3

0.1 F

C4

10 F

+

–15V

C1

10 F

C2

0.1 F

+15V

R3

50

R2

9k

1/4

OP471E

A2

R4

50

R8

50

1/4

OP471E

A4

R7

50

R6

5k

R5

5k

1/4

OP471E

A3

+

Figure 16. High-Output Amplifier