LA 25-P from LEM is a closed loop Hall effect current transducer. It is good for DC, and AC pulse current’s measurements of 25 to 50 ARMS nominal with galvanic isolation.
However, when looking at its connection diagram, you may not immediately understand the functions of the symbol shown below. What is it?
According to the manufacturer directly:
"The symbol in the datasheet connection diagram refers to the op-amp (A; to convert the differential Hall voltage to single-ended) and the totem-pole output stage (which produces the secondary current, Is)…
This is the true topology of closed-loops like the LA 25. The reason for this is 1) to eliminate the gain drift over temperature and 2) to extend the bandwidth of the transducer (ie. via the current transformer effect at higher frequencies).”