Abstract: An arrangement to provide feedback to amplifier systems incorporating an inductive laod. A low value error-sensing resistor is incorporated in conjunction with one or more transistors to provide a feedback correction signal to an amplifier which corrects for distortion caused by both the amplifier and the inductive load. A first embodiment providing a single-ended amplifier system incorporates an error-sensing resistor in series with a transistor, an inductive load and a bias resistor. A negative feedback error signal is provided to the amplifier from a point between the error-sensing resistor and the bias resistor. A second embodiment additionally includes a transformer to isolate the load. The third embodiment provides push-pull amplifier configurations. The third embodiment incorporates two complementary transistors to drive an inductive load. A pick-off arrangement including two capacitors and an error-sensing resistor provides negative feedback to the amplifier.

Abstract: Quantitative data concerning a gem such as a diamond is obtained by irradiating the gem with wide spectrum light. The internal reflections and refractions of this light are picked up and passed through different filters, the output intensity of light from various filters being compared to a reference output from a reference filter. The output data from the examined light provides information as to the quality of the gem.