–12–

REV. 0

OP777

The OP777 can be very useful in many single supply bridge applica-

tions. Figure 49 shows a single supply bridge circuit in which

its output is linearly proportional to the fractional deviation ( )

of the bridge. Note that

=

∆R/R.

+ 2.5V

2R2

=

R1

R1

= 300

REF

192

15V

1M

R1(1+ )

R1

OP777

15V

15V

1M

OP777

10.1k

0.1 F

2.5V

OP777

R2

V2

V1

3

4

REF

192

2

2

10.1k

RG = 10k

R1(1+ )

R1

3

4

6

Figure 49. Linear Response Bridge, Single Supply

In systems, where dual supplies are available, circuit of Figure 50

could be used to detect bridge outputs that are linearly related to

fractional deviation of the bridge.

REF

192

+15V

15V

R1

R2

=

R

R

R2

R1

R

R1

+15V

15V

OP777

OP777

12k

15V

1k

3

2N2222

R(1+ )

OP777

20k

4

Figure 50. Linear Response Bridge

8-Lead SOIC

(R Suffix)

0.1968 (5.00)

0.1890 (4.80)

8

5

4

1

0.2440 (6.20)

0.2284 (5.80)

PIN 1

0.1574 (4.00)

0.1497 (3.80)

0.0688 (1.75)

0.0532 (1.35)

SEATING

PLANE

0.0098 (0.25)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

0.0500

(1.27)

BSC

0.0098 (0.25)

0.0075 (0.19)

0.0500 (1.27)

0.0160 (0.41)

8°

0°

0.0196 (0.50)

0.0099 (0.25)

x 45°

A single supply current source is shown in Figure 51. Large resistors

are used to maintain micropower operation. Output current can be

adjusted by changing the R2B resistor. Compliance voltage is:

VV

V

L

SAT

S

≤−

R1

R2B

R2

= 1mA

11mA

100k

OP777

R2A

97.3k

2.7V TO 30V

10pF

10pF

100k

R2B

2.7k

+

R1 = 100k

R2 = R2A + R2B

Figure 51. Single Supply Current Source

A single supply instrumentation amplifier using two OP777 ampli-

fiers is shown in Figure 52.

2.7V TO 30V

R2 = 1M

OP777

2.7V TO 30V

10.1k

OP777

R1 = 10.1k

1M

V1

V2

V1)

0.02mV

V1

V2

290mV

2mV

29V

USE MATCHED RESISTORS

Figure 52. Single Supply Micropower Instrumentation

Amplifier

8-Lead

SOIC

(RM Suffix)

85

4

1

0.122 (3.10)

0.114 (2.90)

0.199 (5.05)

0.187 (4.75)

PIN 1

0.0256 (0.65) BSC

0.122 (3.10)

0.114 (2.90)

SEATING

PLANE

0.006 (0.15)

0.002 (0.05)

0.018 (0.46)

0.008 (0.20)

0.043 (1.09)

0.037 (0.94)

0.120 (3.05)

0.112 (2.84)

0.011 (0.28)

0.003 (0.08)

0.028 (0.71)

0.016 (0.41)

33

27

0.120 (3.05)

0.112 (2.84)

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).