OP179/OP279

–10–

REV. F

6.2V

6.2V

TRANSMIT

TXA

RECEIVE

RXA

C1

0.1 F

R1

10k

R2

9.09k

2k

P1

TX GAIN

ADJUST

A1

A2

A3

A4

A1, A2 = 1/2 OP279

A3, A4 = 1/2 OP279

R3

55

R4

55

1:1

T1

TO TELEPHONE

LINE

1

2

3

7

6

5

2

3

1

6

5

7

10 F

R7

10k

R8

10k

R5

10k

R6

10k

R9

10k

R14

9.09k

R10

10k

R11

10k

R12

10k

R13

10k

C2

0.1 F

P2

RX GAIN

ADJUST

2k

110

+5V DC

Figure 31. A Single Supply Direct Access Arrangement for

Modems

A Single Supply, Remote Strain Gage Signal Conditioner

The circuit in Figure 32 illustrates a way by which the OP179/

OP279 can be used in a +12 V single supply, 350

Ω strain gage

signal conditioning circuit. In this circuit, the OP179/OP279

serves two functions: (1) By servoing the output of the REF43’s

+2.5 V output across R1, it provides a 20 mA drive to the 350

Ω

strain gage. In this way, small changes in the strain gage pro-

duce large differential output voltages across the AMP04’s in-

puts. (2) To maximize the circuit’s dynamic range, the other

half of the OP179/OP279 is configured as a supply-splitter

connected to the AMP04’s REF terminal. Thus, tension or

compression in the application can be measured by the circuit.

REF43

AMP04

0.1 F

2

6

4

+2.5V

3

1

8

4

2

A1

7

1

8

6

3

2

4

C2

0.1 F

R4

1k

+12V

5

80mV/

COMMON

R1

124

0.1%, LOW TCR

100-ft TWISTED PAIR

BELDEN TYPE 9502

S+

S–

350

STRAIN GAGE

F–

F+

A2

+12V

R2

10k

R3

10k

C1

10 F

7

6

5

+6V

A1, A2 = 1/2 OP279

+12V

20mA DRIVE

Figure 32. A Single Supply, Remote Strain Gage Signal

Conditioner

The AMP04 is configured for a gain of 100, producing a circuit

sensitivity of 80 mV/

Ω. Capacitor C2 is used across the AMP04’s

Pins 8 and 6 to provide a 16-Hz noise filter. If additional noise

across the AMP04’s input to provide differential-mode noise

rejection.

A Single Supply, Balanced Line Driver

The circuit in Figure 33 is a unique line driver circuit topology

used in professional audio applications and has been modified

for automotive audio applications. On a single +12 V supply,

the line driver exhibits less than 0.02% distortion into a 600

Ω

load across the entire audio band (not shown). For loads greater

than 600

Ω, distortion performance improves to where the cir-

cuit exhibits less than 0.002%. The design is a transformerless,

balanced transmission system where output common-mode

rejection of noise is of paramount importance. Like the trans-

former-based system, either output can be shorted to ground for

unbalanced line driver applications without changing the circuit

gain of 1. Other circuit gains can be set according to the equa-

tion in the diagram. This allows the design to be easily config-

ured for noninverting, inverting, or differential operation.

600

C1

22 F

A2

7

6

5

3

1

2

A1

+12V

R1

10k

R2

10k

R11

10k

R7

10k

6

7

5

A1

+12V

+12V

R8

100k

R9

100k

C2

1 F

R12

10k

R14

50

A2

1

2

3

R3

10k

R6

10k

R13

10k

C3

47 F

C4

47 F

A1, A2 = 1/2 OP279

GAIN = R3

R2

SET: R7, R10, R11 = R2

SET: R6, R12, R13 = R3

R5

50

Figure 33. A Single Supply, Balanced Line Driver for

Automotive Applications