Monolithically integratable, low power dissipation control circuit for switching inductive loads

In a switching amplifier for use with an inductive load impedance, wherein said switching amplifier includes two amplifiers, each amplifier having a source stage and a sink stage, wherein an output transistor for each source stage is controlled by a first, second and third transistor and a resistor, a base terminal of said output transistor being coupled to collector terminals of said first and said third transistors, an emitter terminal of first transistor coupled to a positive supply terminal, a collector terminal of said second transistor coupled to a base terminal of said third transistor, an emitter terminal of said third transistor coupled to output terminal of another amplifier, said resistor having one terminal coupled to base terminals of said first and said second transistors, an input signal being coupled to an emitter terminal of said second transistor, the method of reducing power dissipation in said output transistor comprising the step of:

• replacing said second transistor and said resistor with first and second diodes, said diodes having anode terminals coupled to base terminals of said first and said third transistors respectively, said diodes having cathode terminals coupled together and coupled to said input signal.

In a switching amplifier for providing current to an inductive load impedance wherein a base terminal of an output power transistor of a first source stage is coupled to a collector of a first and a second PNP transistors, said first transistor having an emitter terminal coupled to a positive power supply terminal, an emitter terminal of said second transistor coupled to a second sink stage, apparatus for reducing power dissipation in said output power transistor comprising:

• first voltage means for reducing voltage across said output power transistor when said second sink stage is conducting;
• and
• second voltage means for reducing voltage across said output power transistor when said second sink stage is cut off.

In a switching amplifier having a first and a second amplifier, each of said amplifiers having a source stage and a sink stage, wherein an alternating input signal first activates a source stage of one amplifier and a sink stage of the other amplifier and thereafter activates a source stage of said other amplifier and a sink stage of one amplifier, said switching amplifier further including a regulating circuit for disabling a regulating sink stage in response to predetermined conditions, a method of reducing power dissipation in an output power transistor associated with each amplifier comprising the steps of:

• applying said input signal to the cathode terminal of a first diode, said first diode having an anode terminal coupled to a base terminal of a transistor having an emitter terminal coupled to a positive voltage supply terminal and a collector terminal coupled to a base of said power transistors;
• and
• applying a signal resulting from said disabling to an emitter terminal of a second transistor, said second transistor having a collector terminal coupled to said base terminal of said output power transistor, wherein an anode terminal of a second diode is coupled to a base terminal of said second transistor, and wherein a cathode terminal of said second diode is coupled to said first diode cathode terminal.