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An apparatus for detecting a high impedance load on an output of a driver circuit having a power switching circuit providing output signals to a coil. Each output signal results from a drive signal that has a waveform comprising a higher magnitude initial peak period followed by a lower magnitude ho

An apparatus for detecting a high impedance load on an output of a driver circuit having a power switching circuit providing output signals to a coil. Each output signal results from a drive signal that has a waveform comprising a higher magnitude initial peak period followed by a lower magnitude hold period. The driver circuit has a feedback circuit providing a difference signal as a function of a difference between an output signal and a corresponding drive signal. A diagnostic circuit connected to the driver circuit provides a high impedance error signal in response to detecting the difference signal crossing a threshold magnitude during a higher magnitude initial peak period of a drive signal.

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1. An apparatus for use with a fluid dispensing gun having a driver circuit with a load connected thereto, the driver circuit having a power switching circuit providing output signals to a gun coil in the load, each output signal occurring in response to a drive signal having a waveform comprising a

1. An apparatus for use with a fluid dispensing gun having a driver circuit with a load connected thereto, the driver circuit having a power switching circuit providing output signals to a gun coil in the load, each output signal occurring in response to a drive signal having a waveform comprising a higher magnitude initial peak period followed by a lower magnitude hold period, the apparatus comprising:a diagnostic circuit connected to the driver circuit, said diagnostic circuit providing a high impedance error signal in response to detecting during only the higher magnitude initial peak period of the drive signal, a voltage of the output signal exceeding a predetermined value, the high impedance error signal representing a high impedance of the load.