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Maxim > Design Support > Technical Documents > Application Notes > Amplifier and Comparator Circuits > APP 4546
Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 4546
Keywords: high-voltage current monitors, difference amplifiers, adjustable gain, pnp transistors, digital
potentiometers
APPLICATION NOTE 4546
High-Voltage, Programmable-Gain Current Monitor
By: Greg Sutterlin
Cicie Wang
Dec 21, 2010
Abstract: This circuit monitors current flow at high voltage (48V and higher) using a standard 5V
difference amplifier (MAX4198) referenced to ground. It also employs a digital potentiometer (MAX5402)
for gain adjustment.
A similar version of this article appeared in the June 1, 2007 issue of PET.
Telcom, LDMOS, automotive, and numerous other applications require the measurement of current flow
at high voltages (high-side current). Often, a circuit operating at 5V must monitor currents at 48V.
Techniques using costly high-voltage difference amplifiers and other special devices can measure such
currents, but the circuit of Figure 1 does it with a standard 5V difference amp, including provisions for
gain adjustment.
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