Texas Instruments OPA462EVM, User Manual

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Application Circuits
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6 SBOU175 – October 2019
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OPA462EVM
3 Application Circuits
The OPA462EVM may be configured in most standard op amp circuits. See the OPA462 data sheet for
typical applications.
3.1 Improved Howland Current Pump
The OPA462EVM can be configured as an improved Howland current pump that provides an output
current proportional to a single- or differential-input voltage. The improved Howland current pump is
described and analyzed in section 3 of the
A Comprehensive Study of the Howland Current Pump
application report . Information about how the current-pump resistor values are determined for a particular
input voltage and a corresponding output current is provided in the application report. The report
information is applied here in this section as a practical use for the OPA462EVM.
The OPA462EVM, as configured in Figure 1 , sources on an output current of –20 mA when a single-
ended input voltage of 2.5 V is applied to the VP input. If the input voltage sign is reversed, the output
reverses direction and sinks 20 mA. The circuit in
Figure 1 provides the resistance values required to
obtain the correct 20-mA output current. The resistor and capacitor labels correspond to those screened
on the OPA462EVM printed circuit board. As shown in
Figure 1 , when RL is equal to 500 Ω , the sourced
output current level is –20 mA, and Vout is 10 V, as Ohm’s law dictates.
Figure 1. Practical, 20-mA, Improved Howland Current-Pump Circuit
Practical current sources have a limited output voltage range that can be covered. The OPA462 op amp
has a wide output voltage range because of the high-voltage supplies used. The OPA462 data sheet
provides information about the linear output voltage range that should always be observed.