Transient considerations in current sensing especially in motor and solenoids, app note(PDF) from Analog Devices.
Current sense amplifiers are used in a variety of applications, such as motor or solenoid control, load current monitoring, and fault detection. In such applications, it is typical for the input common-mode voltage to swing from ground to a certain highside supply. However, while a user may work with the assumption that the input common-mode swings are limited to this highside supply, there are transient voltages that must be considered. The result of these transients is that a supposed low voltage application tends to appear as a high voltage application, and the current sense amplifier must be robust enough to handle these occurrences.
The courrent flow well, when the gate use a staded of the true gate, but when the gate change the true, the value of the current is opocit to the first staded, and the low.