OP400

Data Sheet

Rev. I | Page 12 of 15

BIPOLAR CURRENT TRANSMITTER

In the circuit of Figure 32, which is an extension of the standard

three op amp instrumentation amplifier, the output current is

proportional to the differential input voltage. Maximum output

current is ±5 mA, with voltage compliance equal to ±10 V when

using ±15 V supplies. Output impedance of the current transmitter

exceeds 3 MΩ, and linearity is better than 16 bits with gain set

for a full-scale input of ±100 µV.

DIFFERENTIAL OUTPUT INSTRUMENTATION

AMPLIFIER

The output voltage swing of a single-ended instrumentation

amplifier is limited by the supplies, normally at ±15 V, to a

maximum of 24 V p-p. The differential output instrumentation

amplifier shown in Figure 33 can provide an output voltage

swing of 48 V p-p when operated with ±15 V supplies. The

extended output swing is due to the opposite polarity of the

outputs. Both outputs swing 24 V p-p, but with opposite polarity,

for a total output voltage swing of 48 V p-p. The reference input can

set a common-mode output voltage over the range ±10 V. The

PSRR of the amplifier is less than 1 µV/V with CMRR (G = 1000)

better than 115 dB. Offset voltage drift is typically 0.4 µV/°C over

the military temperature range.

–

+

VOUT

IOUT

5mA

IOUT

VIN

50,000

200Ω

200Ω

RG

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

RG

–

–

1

VIN

1/4

OP400E

+

–

1/4

OP400E

+

–

1/4

OP400E

+

–

1/4

OP400E

+

–

Figure 32. Bipolar Current Transmitter

–

+

VOUT

VIN

RG

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

22pF

22pF

22pF

22pF

25kΩ

25kΩ

25kΩ

VOUT

VIN

=

50kΩ + RG

RG

REFERENCE

INPUT

1/4

OP400A

+

–

1/4

OP400A

+

–

1/4

OP400A

+

–

1/4

OP400A

+

–

Figure 33. Differential Output Instrumentation Amplifier