OP400

Rev. E | Page 12 of 16

BIPOLAR CURRENT TRANSMITTER

In the circuit of Figure 31, 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 instrumenta-

tion amplifier shown in Figure 32 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 be used to 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.

–

+

5mA

50,000

200Ω

200Ω

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

––

1

1/4

OP400E

+

–

1/4

OP400E

+

–

1/4

OP400E

+

–

1/4

OP400E

+

–

Figure 31. Bipolar Current Transmitter

–

+

25kΩ

25kΩ

25kΩ

25kΩ

25kΩ

22pF

22pF

22pF

22pF

25kΩ

25kΩ

25kΩ

=

REFERENCE

INPUT

1/4

OP400A

+

–

1/4

OP400A

+

–

1/4

OP400A

+

–

1/4

OP400A

+

–

Figure 32. Differential Output Instrumentation Amplifier