Importance

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Abstract

A current feedback amplifier (12) is provided for controlling a stator winding phase current in a polyphase stator winding, such as a three-phase stator winding (10), of a polyphase direct current motor. The current amplifier (12) includes a first stage current feedback amplifier C (27) and a second stage current feedback amplifier (100) coupled through a switch (101). The first stage current feedback amplifier C (27) detects a stator winding phase current I.sub.AB flowing through a C-coil (15) of the three-phase stator winding (10) and generates an equalized sense current I.sub.senseT in response that is related to I.sub.AB. The equalized sense current I.sub.senseT is generated using a phase trim FET (31) and an adjustable phase trim FET (32). The second stage current feedback amplifier (100) receives I.sub.senseT from the first stage current feedback amplifier C (27) and generates a control signal. This may be done by comparing I.sub.senseT to an amplitude adjusted reference current I.sub.refT. The amplitude adjusted reference current I.sub.refT is generated using an amplitude trim FET (81) and an adjustable amplitude trim FET (82). The second stage current feedback amplifier (100) provides the control signal to a driver circuit for controlling the stator winding phase current. The second stage current feedback amplifier (100) may sequentially or commutatively couple to other first stage current sense amplifiers, such as a first stage current feedback amplifier B (30) or a first stage current feedback amplifier A (28), to control other stator winding phase currents to generate equalized, amplitude adjusted stator winding phase currents.

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First Claim