What is the 'sense' pin on an op-amp for and how is it used?

What are some circuit examples that that use the sense pin?

Here is an example of an op-amp with a sense pin: http://www.ti.com/lit/ds/symlink/ina137.pdf

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    \$\begingroup\$ That isn't an opamp, it is an instrumentation amplifier. The sense pin in these amplifiers is meant to be connected to the output in order to compensate for any voltage drop across the output pin resistance. \$\endgroup\$ – Evan Feb 3 '17 at 4:26
  • \$\begingroup\$ If one connects pins 1 and 3, that's a high-Z positive input. Connect pins 2 and 5, that's a high-Z negative input. Output is presumably low impedance, and it works with feedback. Op amp is as good a description as instrumentation amplifier. \$\endgroup\$ – Whit3rd Feb 3 '17 at 5:24
  • \$\begingroup\$ Quote from the reference given by OP - "The INA137 and INA2137 are differential line receivers consisting of high performance op amps with on-chip precision resistors." I.e. they are not op amps but prebuilt circuits that contain op amps. \$\endgroup\$ – JIm Dearden Feb 3 '17 at 10:31
  • \$\begingroup\$ Opamps are generally three-terminal (+in, -in, out). You supply a feedback path. In general, when you see a "sense" option, the device's feedback path is available to you, but is normally strapped to the device's output. For a review of how external sensing is used:ti.com/lit/an/slyt467/slyt467.pdf \$\endgroup\$ – glen_geek Feb 3 '17 at 14:41

The sense pin in a voltage regulator is connected to the point-of-load so that a high output current and wiring resistance do not compromise the voltage regulation. The INA137 sense pin serves a similar purpose, allowing the amplifier output to be sensed, for feedback, at an output node which might not be directly wired to the amplifier 'output' pin. see figure 5

The matching of the internal resistors is better than easily achievable with discrete components, so a variety of precision circuits is possible with this kind of packaged op-amp/resistor array. Someone chose 'sense' as a descriptive label for the low-R inverting input connection, possibly because it can replicate the function of voltage sense wiring.

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  • \$\begingroup\$ Right. So if the voltage drops at the output pin or at some other point, such as in figure 5 above, then the sense pin 'senses' the drop and compensates by changing the resistance and therefore keeping the voltage at the same level? is that correct? But what if the output is AC? \$\endgroup\$ – Ryan Ashton Feb 3 '17 at 5:10
  • \$\begingroup\$ AC, DC; no difference. There's no explicit frequency dependence. \$\endgroup\$ – Whit3rd Feb 3 '17 at 5:19
  • \$\begingroup\$ What I mean is that with AC voltage always fluctuating according to its frequency, how does the sensing work? \$\endgroup\$ – Ryan Ashton Feb 3 '17 at 5:36
  • \$\begingroup\$ If you want an amplifier to deliver regulated AC, it has to have a reference AC source, and amplify it. Unless the amplifier overloads, the output can be sensed and corrected to a fixed multiple of the input, according to resistor ratios. \$\endgroup\$ – Whit3rd Feb 3 '17 at 6:45

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