MPX stereo signal demodulator

An MPX stereo signal demodulator comprising:

• A. a direct voltage source;
• B. a first differential amplifier including at least a first pair of transistors and a common emitter impedance connected to a reference voltage point;
• C. a second differential amplifier including at least a second pair of transistors with the emitters thereof connected to each other and to the collector of one of the transistors of said first differential amplifier;
• D. a third differential amplifier including at least a third pair of transistors with the emitters thereof connected to each other and to the collector of the other transistor of said first differential amplifier;
• E. coupling circuit means for coupling the collector of one of the transistors of said second differential amplifier to a first connection point comprising the collector of one of the transistors of said third differential amplifier and coupling the collector of the other transistor of said second differential amplifier to a second connection point comprising the collector of the other transistor of said third differential amplifier, respectively, said connection point comprising a pair of signal output terminals;
• F. a fourth differential amplifier including at least a fourth pair of transistors and a common emitter impedance connected to the reference voltage point;
• G. current mirror circuit means connected between said direct voltage source and collector circuits of said second, third and fourth differential amplifiers;
• H. signal input means for applying a composite stereo signal to said first and fourth differential amplifiers and for applying a subcarrier signal to said second and third differential amplifiers, respectively;
• and
• I. means for varying the composite signal levels applied to said first and fourth differential amplifiers, relatively, so as to adjust separation characteristics between the output signals at said signal output terminals.