A control circuit for linear motors driving pumps or compressors that provides a programmable pressure versus flow behavior. The duty cycle of a pulse width modulated drive signal to a coil in the motor is controlled by a parameter determined by the shape of the back EMF signal generated by that coil when it is not driven. The measured parameter value is compared to a target value for the present drive pulse width, and the pulse width is adjusted to reduce the difference between the measured value and the target value. The target value is stored in a table of calibrated values that determines the desired pressure versus flow behavior and can also compensate for manufacturing differences between individual pumps.