OP400

–9–

REV. A

BIPOLAR CURRENT TRANSMITTER

In the circuit of Figure 5, 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 transmit-

ter exceeds 3 M

W and linearity is better than 16 bits with gain

set for a full scale input of

±100 mV.

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 of Figure 6 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 will 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. PSRR of the amplifier is less than 1 mV/V with CMRR

(G = 1000) better than 115 dB. Offset voltage drift is typically

0.4

mV/∞C over the military temperature range.

Figure 6. Differential Output Instrumentation Amplifier

Figure 5. Bipolar Current Transmitter