Apparatus and method for noise suppression in a balanced modulating device

摘要

A circuit and method are shown for suppressing a common-mode noise signal in a pair of differential balanced-modulated color signals. A complementary balanced-modulated color signal, which includes the common-mode noise signal, inverse modulates a first current in a first transistor which is connected in series with a second transistor. The second transistor sinks a second current responsive to a common base current. A balanced-modulated color signal, which also includes the common-mode noise signal, inverse modulates the current in a third transistor which is connected in series with a fourth transistor. The fourth transistor sinks a fourth current responsive to the common base current. The common base current is produced by driving a fifth transistor with the first current less the second current signal. An output signal that is free of the common mode noise signal is produced by subtracting the fourth current from the third current.