Application Circuits; Improved Howland Current Pump; Practical, 20-Ma, Improved Howland Current-Pump Circuit - Texas Instruments OPA462 User Manual

Application Circuits

3 Application Circuits
The OPA462EVM may be configured in most standard op amp circuits. See the
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
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
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
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
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.
6
OPA462EVM
A Comprehensive Study of the Howland Current Pump
Figure 1, sources on an output current of –20 mA when a single-
Figure 1
Figure
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OPA462 data sheet
provides the resistance values required to
1, when RL is equal to 500 Ω, the sourced
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