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OPA4376-Q1: OPA4376-Q1 outputs an error voltage when it is close to zero input

user5397585
Prodigy 110 points
Part Number: OPA4376-Q1
Other Parts Discussed in Thread: OPA4376

When using OPA4376, we have the following problem:

using a single 5V power supply, applying about 2500 voltages to the non-inverting and inverting terminals, and the inverting terminal is 1mV or 2mV higher than the non-inverting terminal.

The op amp output voltage jumps around 160mV.

1. During static test, a fixed voltage of 2502mV and 2500mV is applied to the inverting terminal and the copper image terminal respectively, and the output result is a fixed value of 1mV (theoretical is 0mV), and the output is correct.

2. When we apply our signal source, the system transient, applying a voltage of about 2500 on the non-inverting and inverting terminals, the inverting terminal is 1mV or 2mV higher than the non-inverting terminal. The op amp output voltage jumps around 160mV. The output is incorrect.

  • 0
    Guru 140200 points

    Hi,

    what do you mean by "system transient"? Can you give a scope plot showing the input signal and output signal? It should also show the 160mV voltage jump.

    Kai

  • 0
    TI__Guru* 93105 points

    Hi user5397585,

    What tolerance resistors are you using throughout the entire OPA4376 circuit? If the resistor tolerances are high and the resistance values are not well matched there can be unequal gains produced through the two input amplifiers and difference amplifier stage signal paths.

    If you do the gain calculations based on worst case resistor tolerances you will be surprised by the error levels for 1 %, and even 0.1% resistors. That is why precision instrumentation amplifiers exists. They have on-board resistors that are laser trimmed to within milliohms of each other. The end result is they have precise gain and very high common-mode rejection (CMRR).

    Regards, Thomas

    Precision Amplifiers Applications Engineering