Abstract: A source of driving signals is coupled to a thermal transducer wire to provide a completed circuit. The source may include a DC bias supply and an audio amplifier. The bias supply heats the wire to a predetermined temperature, and the amplifier heats and cools the wire above and below the predetermined temperature. The wire expands and contracts in response to the audio signals, thus providing for acoustic reproduction thereof. The wire may be coupled to a diaphragm, such as a conventional speaker cone, to accomplish the acoustic reproduction. A lever arrangement coupled between the wire and the diaphragm may be employed to obtain increased diaphragm motion. A lever arrangement employing two wires in a push-pull configuration is also provided for obtaining increased motion. Additionally, a true RMS meter and a relay are provided which incorporate the heated wire thermal motion arrangement.

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: An arrangement to provide feedback to amplifier systems incorporating an electrical load. A current transformer in conjunction with a resistor is incorporated 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 provides a single-ended amplifier driving a load and incorporates the current transformer between the output of the amplifier and the load. The secondary winding of the transformer is in series with the input to the amplifier, and a resistor is connected across the secondary winding. The transformer determines the frequency bandwidth of the entire amplifier system, and the resistor value determines the gain of the amplifier. Such a configuration provides negative feedback to the amplifier which is directly proportional to changes in current in the load due to distortions caused by the amplifier or load.