Complementary push-pull amplifier device with protective circuit means

In a complementary push-pull amplifier device with protective circuit means including at least a driving amplifier circuit and a push-pull output circuit connected to the output of said driving amplifier circuit, the push-pull output circuit consisting of a first amplifier portion and a second amplifier portion, wherein inputs of said first and second amplifier portions are respectively connected to the output of said driving amplifier circuit,

• so that said first amplifier portion is rendered conductive and said second amplifier portion is rendered non-conductive respectively when the drive current of said driving amplifier circuit decreases, and said first amplifier portion is rendered non-conductive and said second amplifier portion is rendered conductive when the drive current of said driving amplifier circuit increases, the improvement comprising:
• a first detecting circuit connected in series with said first amplifier portion between a first d.c. voltage source and an output juncture of said push-pull output circuit;
• a second detecting circuit connected in series with said second amplifier portion between said output juncture of said push-pull output circuit and a second d.c. voltage source;
• first protective circuit means, connected to the input of said first amplifier portion and responsive to a first detected signal of said first detecting circuit, for controlling the input of said first amplifier portion, when said first amplifier portion falls out of its allowable operating range;
• and
• second protective circuit means, connected to the input of said driving amplifier circuit and responsive to a second detected signal of said second detecting circuit, for controlling the input of said second amplifier portion when said second amplifier portion falls out of its allowable operating range.