Abstract: A drive arrangement for the shaft of a turbo molecular pump comprises a motor supply, including a chopper which controls a voltage source, and a motor with two phase windings connected via a current measuring resistor to the neutral point of the voltage source. The voltage drop at the resistor is proportional to the motor current and so influences the width of the control pulses of a pulse-width modulator connected to control the chopper that the motor current remains constant. Switching transistors for the motor have parallel oppositely-connected diodes which, upon disconnection of a phase winding, supply residual energy to capacitors in the circuit.