Balanced line signal linear amplitude modulator using a magnetic resistance bridge sensor

摘要

A balanced line (3) signal linear amplitude modulator, comprising a giant magnetic resistance (GMR) bridge sensor (8), magnetically coupled with and controlled by a single voltage controlled magnetic coil (10). The amplitude modulator is not electrically coupled to the coil, which reduces noise and distortion, as no DC voltage is connected to the GMR sensor. The primary application is for audio and video signal processing use. It is not for use as a logic gate. The GMR bridge sensor is not being employed as a differential amplifier, but as a balanced line input to output attenuator. As the bridge is DC isolated and is run at high level, with balanced input signals, it produces very low noise and distortion. The voltage controlled coil driver amplifier employs a negative feedback path for precise isolated control, with considerably reduced ringing and kickback effects associated with DC magnets. A biasing magnet may be placed above the GMR sensor bridge to reduce hysteresis effects of the GMR sensor bridge.