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Measure voltage of -60 to +60 volts accurately using operationnal amplifiers

Other Parts Discussed in Thread: OPA192, TIPD130, INA826

Hello,

I want to sense high positive and negative DC voltage that variates from -60 to +60 using highi accuracy operationnal amplifier.

I'm thinking about using differential attenuator with a level shifting...

I don't  if there is a normalized circuit for that and which TI op amp i can use ?

Thank you,

  • Hello Yassine,

    You don't mention if you intended to use a dual, or single supply to power your op amp circuit. That can make a difference in the approach you take. Also, I am under the impression that you wish to reduce the +/-60 V level to something lower.

    If you are using dual supplies such as +/-15 V, then a simple buffered voltage divider can be used to reduce the voltage to a lower bipolar level such as +/-10 V. I show an example here where a voltage divider takes the +/-60 V and divides it down to +/-10 V. The OPA192 buffers the voltage divider and contributes very little in the ways of errors to the divided down voltage. Most of the inaccuracy will come from the R1, R2 resistor tolerances and temperature coefficients.

    If you wish to use a single supply an approach you can take is to use a divider/ level shift circuit and follow it with a single-supply instrumentation amplifier. The input range could be set up for +/-60 V and output could be set up for a convenient range such as 0 to +3 V, or 0 to + 5V. A few years ago I created a TI Precision Design (TIPD) where I used that approach with a comparator. It is TIPD130 and the input networks can be applied to linear circuits as well. The TIPD covers the details as to how the resistors in the networks are calculated.

    The TIPD130 title is, "Dual Polarity High-Voltage Differential Interface for Low-Voltage Comparators Reference Design." It uses a specially designed 3-resistor networks at each input to establish the desired input voltage range and a specific input offset such that the output is scaled to a particular voltage range. This interface would work nicely with an instrumentation amplifier and could be set up with differential inputs.

    The INA826 offers a lot of flexibility in terms of supply voltage, low input bias current and low operating current. You can view its datasheet via this link:

    I hope this is of help to you.

    Regards, Thomas

    Precision Amplifiers Applications Engineering