Systems, methods, and circuits for reducing HUM modulation in amplifiers

An amplifier, comprising:

• a gain stage for amplifying an input signal and for generating an output signal;
• a bypass coil;
• a shunt capacitor associated with the gain stage that is physically and magnetically coupled to the bypass coil, the shunt capacitor having a linear region of operation in which an electric flux density essentially varies linearly with an applied electric field and a non-linear region defined by a hysteresis loop;
• and
• a resistance connected in series with the shunt capacitor for dissipating energy;
• wherein the resistance reduces energy stored in the shunt capacitor and reduces a range over which an impedance of the shunt capacitor varies, thereby improving performance of the amplifier with respect to hum modulation.

A method of reducing hum modulation in a communication system, comprising:

• amplifying an input signal and providing an amplified output signal, wherein amplifying the input signal includes using a bypass coil to reduce current variations;
• filtering transient voltages during the amplifying of the input signal, the filtering comprising using a capacitor;
• connecting a resistance in series with the capacitor;
• and
• dissipating, with the resistance, energy that normally would pass through the capacitor, wherein dissipating includes dissipating energy transferred from the bypass coil to the capacitor;
• wherein the dissipating of the energy reduces a range within which an impedance associated with the capacitor varies and improves a performance of the communication system with respect to hum modulation.