Amplifier with over-current protection

Claim 2

An amplifier with over-current protection comprising: an input terminal for receiving an input signal current; an output terminal for connection to a load; a common terminal for connection to an operating potential; transistor means having a base electrode connected to said input terminal, having a collector electrode connected to said output terminal, and having an emitter electrode; a resistive element connecting the emitter electrode of said transistor means to said common terminal and responsive to the emitter current of said transistor means to develop a potential proportional to that current between said common terminal and said emitter electrode; a source providing a potential with reference to said common terminal, which potential is responsive to the temperature of said transistor means so as to decrease with increasing temperature; and a unilaterally conductive device connecting said source to the base electrode of said transistor means, the direction of relatively easy conduction through said device being such as to limit the excursion of signal potential appearing responsive to said input signal current between the base electrode of said transistor means and said common terminal.

Claim 3

An amplifier with over-current protection as set forth in claim 1 wherein said transistor means is a composite transistor including: first and second component transistors of complementary conductivity types, each of said component transistors having base and emitter and collector electrodes, the base electrode of said first component transistor being connected to said input terminal to provide the base electrode of said composite transistor, the collector electrode of said first component transistor being connected to the base electrode of said second component transistor, the emitter electrode of said second component transistor providing the collector electrode of said composite transistor, and the collector electrode of said second component transistor being connected to the emitter electrode of said first component transistor, which provides the emitter electrode of said composite transistor.

Claim 4

An amplifier with over-current protection as set forth in claim 2 including at least one further transistor with a base electrode to which the collector electrode of said first component transistor is connected, with an emitter electrode connected to said output terminal, and with a collector electrode connected to said common terminal.

Claim 5

An amplifier with over-current protection comprising: an input terminal for receiving an input signal current; an output terminal for connection to a load; a common terminal for connection to an operating potential; transistor means having a base electrode connected to said input terminal, having a collector electrode connected to said output terminal, and having an emitter electrode; a resistive element with substantially constant resistance connecting the emitter electrode of said transistor means to said common terminal and responsive to the emitter current of said transistor means to develop a potential proportional to that current between said common terminal and said emitter electrode; a source providing a potential with reference to said common terminal, which potential is responsive to said operating potential so as to decrease as said operating potential decreases below a threshold potential; and a unilaterally conductive device connecting said source to the base electrode of said transistor means, the direction of relatively easy conduction through said device being such as to limit the excursion of signal potential appearing responsive to said input signal current between the base electrode of said transistor means and said common terminal.

Claim 6

An amplifier with over-current protection comprising: an input terminal for receiving an input signal current; an output terminal for connection to a load; a common terminal for connection to an operating potential; transistor means having a base electrode connected to said input terminal, having a collector electrode connected to said output terminal, and having an emitter electrode; a resistive element with substantially constant resistance connecting the emitter electrode of said transistor means to said common terminal and responsive to the emitter current of said transistor means to develop a potential proportional to that current between said common terminal and said emitter electrode; a source providing a potential with reference to said common terminal, which potential is responsive to said operating potential so as to decrease as said operating potential decreases below a threshold potential; and a unilaterally conductive device connecting said source to the base electrode of said transistor means, the direction of relatively easy conduction through said device being such as to limit the excursion of signal potential appearing responsive to said input signal current between the base electrode of said transistor means and said common terminal.

Claim 7

An amplifier with over-current protection as set forth in claim 4 wherein said transistor means is a composite transistor including: first and second component transistors of complementary conductivity types, each of said component transistors having base and emitter and collector electrodes, the base electrode of said first component transistor being connected to said input terminal to provide the base electrode of said composite transistor, the collector electrode of said first component transistor being connected to the base electrode of said second component transistor, the emitter electrode of said second component transistor providing the collector electrode of said composite transistor, and the collector electrode of said second component transistor being connected to the emitter electrode of said first component transistor, which provides the emitter electrode of said composite transistor.

Claim 8

An amplifier with over-current protection as set forth in claim 5 including at least one further transistor with a base electrode to which the collector electrode of said first component transistor is connected, with an emitter electrode connected to said output terminal, and with a collector electrode connected to said common terminal.

Claim 9

An amplifier with over-current protection comprising: an input terminal for receiving an input signal current; an output terminal for connection to a load; a common terminal for connection to an operating potential; transistor means having a base electrode connected to said input terminal, having a collector electrode connected to said output terminal, and having an emitter electrode; a resistive element connecting the emitter electrode of said transistor means to said common terminal and responsive to the emitter current of said transistor means to develop a potential proportional to that current between said common terminal and said emitter electrode; a source providing a potential with reference to said common terminal, which potential is responsive to said energizing potential so as to decrease as said energizing potential decreases below a threshold potential, and is responsive to the temperature of said transistor means so as to decrease as said temperature increases; and a first unilaterally conductive device connecting said source to the base electrode of said first transistor means, the direction of relatively easy conduction through said device being such as to limit the excursion of signal potential appearing responsive to said input signal current between the base electrode of said transistor means and said common terminal.

Claim 10

An amplifier with over-current protection comprising: an input terminal for receiving an input signal current; an output terminal for connection to a load; a common terminal for connection to an operating potential; transistor means having a base electrode connected to said input terminal, having a collector electrode connected to said output terminal, and having an emitter electrode; a resistive element connecting the emitter electrode of said transistor means to said common terminal and responsive to the emitter current of said transistor means to develop a potential proportional to that current between said common terminal and said emitter electrode; a source providing a potential with reference to said common terminal, which potential is responsive to said energizing potential so as to decrease as said energizing potential decreases below a threshold potential, and is responsive to the temperature of said transistor means so as to decrease as said temperature increases; and a first unilaterally conductive device connecting said source to the base electrode of said first transistor means, the direction of relatively easy conduction through said device being such as to limit the excursion of signal potential appearing responsive to said input signal current between the base electrode of said transistor means and said common terminal.

Claim 11

An amplifier with over-current protection as set forth in claim 7 wherein said transistor means is a composite transistor including: first and second component transistors of complementary conductivity types, each of said component transistors having base and emitter and collector electrodes, the base electrode of said first component transistor being connected to said input terminal to provide the base electrode of said composite transistor, the collector electrode of said first component transistor being connected to the base electrode of said second component transistor, the emitter electrode of said second component transistor providing the collector electrode of said composite transistor, and the collector electrode of said second component transistor being connected to the emitter electrode of said first component transistor, which provides the emitter electrode of said composite transistor.

Claim 12

An amplifier with over-current protection as set forth in claim 8 including at least one further transistor with a base electrode to which the collector electrode of said first component transistor is connected, with an emitter electrode connected to said output terminal, and with a collector electrode connected to said common terminal.

Claim 13

An amplifier with over-current protection comprising: an input terminal, an output terminal and a common terminal, said output and common terminals for providing an output current responsive to an input current received between said input and common terminals; a first transistor of a first conductivity type having a base electrode coupled to said input terminal and having an emitter and a collector electrode; a second transistor of a second conductivity type having a base electrode direct coupled from said first transistor collector electrode, having an emitter electrode direct current conductively coupled to said output terminal, and having a collector electrode to which said first emitter electrode is direct coupled; means for limiting the range of potential excursions appearing between said first transistor base electrode and said common terminal, which potential excursions occur responsive to said input current; a resistive element coupling said second transistor collector electrode to said common terminal and proportionally responsive to collector current of said second transistor to develop a potential proportional to that current between said first transistor base electrode and said common terminal; and at least one further transistor of said second conductivity type having a base electrode direct coupled from said first transistor collector electrode, an emitter electrode direct current conductively coupled to said output terminal, and a collector electrode direct current conductively coupled to said common terminal other than through said resistive element.

Claim 14

An amplifier with over-current protection comprising: an input terminal, an output terminal and a common terminal, said output and common terminals for providing an output current responsive to an input current received between said input and common terminals; a first transistor of a first conductivity type having a base electrode coupled to said input terminal and having an emitter and a collector electrode; a second transistor of a second conductivity type having a base electrode direct coupled from said first transistor collector electrode, having an emitter electrode direct current conductively coupled to said output terminal, and having a collector electrode to which said first emitter electrode is direct coupled; means for limiting the range of potential excursions appearing between said first transistor base electrode and said common terminal, which potential excursions occur responsive to said input current; a resistive element coupling said second transistor collector electrode to said common terminal and proportionally responsive to collector current of said second transistor to develop a potential proportional to that current between said first transistor base electrode and said common terminal; and at least one further transistor of said second conductivity type having a base electrode direct coupled from said first transistor collector electrode, an emitter electrode direct current conductively coupled to said output terminal, and a collector electrode direct current conductively coupled to said common terminal other than through said resistive element.

Claim 15

An amplifier as claimed in claim 10 wherein said means for limiting excursions of potential comprises: means providing a source of potential offset from said common terminal and an assymmetrically conductive element coupled between said means for providing a source of offset potential and said first transistor base electrode.

Claim 16

An amplifier as claimed in claim 11 wherein said assymmetrically conductive element comprises a semiconductor junction.

Claim 17

The combination of: a composite transistor comprising a plurality of transistors of one conductivity type connected base-to-base, connected emitter-to-emitter to an output terminal, and all except one connected collector-to-collector to an operating voltage terminal, and an input transistor of another conductivity type connected at its collector to all of said bases, at its base to an input signal terminal, and at its emitter to the collector of said one of said plurality of transistors; a current sensing element connected between said emitter of said input transistor and said operating voltage terminal; and means responsive to the sensing by said element of more than a given level of current for limiting to a given value the potential at said input signal terminal.

Claim 18

The combination of: a composite transistor comprising a plurality of transistors of one conductivity type connected base-to-base, connected emitter-to-emitter to an output terminal, and all except one connected collector-to-collector to an operating voltage terminal, and an input transistor of another conductivity type connected at its collector to all of said bases, at its base to an input signal terminal, and at its emitter to the collector of said one of said plurality of transistors; a current sensing element connected between said emitter of said input transistor and said operating voltage terminal; and means responsive to the sensing by said element of more than a given level of current for limiting to a given value the potential at said input signal terminal.

Claim 19

The combination as set forth in claim 13, wherein said current sensing means comprises a resistor.

Claim 20

The combination as set forth in claim 13, further including means coupled to said operating voltage terminal for providing at a second operating voltage terminal a voltage offset with respect thereto; and wherein said means responsive to the sensing by said element of more than a given level of current comprises a diode connected between said second operating voltage terminal and said base electrode of said input transistor, poled to conduct in the forward direction when voltage at said base tends to differ from that at said second operating voltage terminal by more than a given amount.