OP179/OP279
–10–
REV. G
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
ZO
110
5V DC
Figure 10. A Single-Supply Direct Access Arrangement for
Modems
A Single-Supply, Remote Strain Gage Signal Conditioner
The circuit in Figure 11 illustrates a way by which the OP179/
OP279 can be used in a 12 V single supply, 350
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
strain gage. In this way, small changes in the strain gage pro-
duce large differential output voltages across the AMP04’s
inputs. (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
CX
C2
0.1 F
R4
1k
12V
5
VO
80mV/
VO
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 11. A Single-Supply, Remote Strain Gage Signal
Conditioner
The AMP04 is configured for a gain of 100, producing a circuit
sensitivity of 80 mV/
. Capacitor C2 is used across the AMP04’s
Pins 8 and 6 to provide a 16-Hz noise filter. If additional noise
filtering is required, an optional capacitor, CX, can be used across
the AMP04’s input to provide differential-mode noise rejection.
A Single-Supply, Balanced Line Driver
The circuit in Figure 12 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
load
across the entire audio band (not shown). For loads greater than
600
, distortion performance improves to where the circuit
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 transformer-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 equation in the
diagram. This allows the design to be easily configured for
noninverting, inverting, or differential operation.
RL
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
R8
100k
R9
100k
C2
1 F
R12
10k
R14
50
A2
1
2
3
R3
10k
R6
10k
R13
10k
C3
47 F
VO1
VO2
C4
47 F
A1, A2 = 1/2 OP279
GAIN = R3
R2
SET: R7, R10, R11 = R2
SET: R6, R12, R13 = R3
VIN
R5
50
Figure 12. A Single-Supply, Balanced Line Driver for
Automotive Applications