Overvoltage and overcurrent protective circuit for a transistor amplifier

Claim 2

An overvoltage and overcurrent protective circuit for a transistor amplifier having an input and an output, comprising: deriving means for deriving a first voltage proportionate to current flowing through said transistor amplifier and a second voltage proportionate to the voltage applied to said transistor amplifier; a protective transistor connected to the input of said transistor amplifier and having an input and an output; coupling means for applying said first and second voltages to the input of said protective transistor in a manner whereby when the difference between said voltages reaches a predetermined magnitude said magnitude switches said protective transistor to its conductive condition to switch said transistor amplifier to its nonconductive condition; and a diode connected in the output of said transistor amplifier for impeding an increase in voltage applied to said transistor amplifier upon a decrease in current flowing through said transistor amplifier in Class A operation.

Claim 3

An overvoltage and overcurrent protective circuit for a transistor amplifier having an input and an output including emitter, collector and base electrodes, comprising: deriving means for deriving a first voltage proportionate to current flowing through said transistor amplifier and a second voltage proportionate to the voltage applied to said transistor amplifier; a protective transistor connected to the input of said transistor amplifier and having an input and an output including emitter, collector and base electrodes; coupling means for applying said first and second voltages to the input of said protective transistor in a manner whereby the difference between said voltages reaches a predetermined magnitude said magnitude switches said protective transistor to its conductive condition to switch said transistor amplifier to its nonconductive condition; a load; a source of supply voltage having one terminal connected to the emitter electrode of said protective transistor and another terminal of opposite polarity connected to the collector electrode of said transistor amplifier through said load; and means directly connecting the collector electrode of said protective transistor to the base electrode of said transistor amplifier.

Claim 4

An overvoltage and overcurrent protective circuit for a transistor amplifier having an input and an output including emitter, collector and base electrodes, comprising: deriving means for deriving a first voltage proportionate to current flowing through said transistor amplifier and a second voltage proportionate to the voltage applied to said transistor amplifier; a protective transistor connected to the input of said transistor amplifier and having an input and an output including emitter, collector and base electrodes; coupling means for applying said first and second voltages to the input of said protective transistor in a manner whereby the difference between said voltages reaches a predetermined magnitude said magnitude switches said protective transistor to its conductive condition to switch said transistor amplifier to its nonconductive condition; a load; a source of supply voltage having one terminal connected to the emitter electrode of said protective transistor and another terminal of opposite polarity connected to the collector electrode of said transistor amplifier through said load; and means directly connecting the collector electrode of said protective transistor to the base electrode of said transistor amplifier.

Claim 5

An overvoltage and overcurrent protective circuit for a single ended push-pull transistor amplifier having a negative feedback circuit and an input and an output comprising: deriving means for deriving a first voltage proportionate to current flowing through said transistor amplifier and a second voltage proportionate to the voltage applied to said transistor amplifier; protective transistors connected to the input of said transistor amplifier and having an input and an output; a transistor coupled to the inputs of said protective transistors for providing suitable values for the gain and phase of the negative feedback circuit of said single ended push-pull transistor amplifier; and coupling means for applying said first and second voltages to the input of said protectiVe transistor in a manner whereby when the difference between said voltages reaches a predetermined magnitude said magnitude switches said protective transistors to their conductive condition to switch said transistor amplifier to its nonconductive condition, said coupling means including detector means for detecting the voltage difference magnitude and control circuit means coupling said detector means to said transistor for controlling the operation of said transistor.

Claim 6

An overvoltage and overcurrent protective circuit for a single ended push-pull transistor amplifier having a negative feedback circuit and an input and an output comprising: deriving means for deriving a first voltage proportionate to current flowing through said transistor amplifier and a second voltage proportionate to the voltage applied to said transistor amplifier; protective transistors connected to the input of said transistor amplifier and having an input and an output; a transistor coupled to the inputs of said protective transistors for providing suitable values for the gain and phase of the negative feedback circuit of said single ended push-pull transistor amplifier; and coupling means for applying said first and second voltages to the input of said protectiVe transistor in a manner whereby when the difference between said voltages reaches a predetermined magnitude said magnitude switches said protective transistors to their conductive condition to switch said transistor amplifier to its nonconductive condition, said coupling means including detector means for detecting the voltage difference magnitude and control circuit means coupling said detector means to said transistor for controlling the operation of said transistor.

Claim 7

An overvoltage and overcurrent protective circuit as claimed in claim 3, further comprising a power supply coupled to said push-pull amplifier and a source of power connectable to said power supply and wherein said control circuit means includes a time constant circuit having a time constant which prevents the push-pull transistor amplifier from being switched to its nonconductive condition when said source of power is connected to said power supply immediately after said push-pull amplifier is switched to its nonconductive condition while a voltage is applied to said push-pull amplifier.

Claim 8

An overvoltage and overcurrent protective circuit as claimed in claim 4, wherein said time constant circuit comprises a capacitor and a resistor connected in series circuit arrangement and a diode connected between a common point in the connection between said capacitor and said resistor and a point at ground potential.

Claim 9

An overvoltage and overcurrent protective circuit as claimed in claim 1, further comprising a first resistor connected between the emitter electrode of said transistor amplifier and said one terminal of said source of supply voltage, a capacitor and a variable resistor connected in series circuit arrangement between the collector electrode of said transistor amplifier and said one terminal of said source of supply voltage, said variable resistor having a slidable tap.

Claim 10

An overvoltage and overcurrent protective circuit as claimed in claim 6, further comprising a second resistor and a diode connected in series circuit arrangement between the emitter electrode of said transistor amplifier and the slidable tap of said variable resistor and means connecting the base electrode of said protective transistor to a common point in the connection between said second resistor and said diode.