Coupling circuit

Claim 2

The combination comprising: first and second points for the application therebetween of an operating potential; a transistor having a base, an emitter and a collector; means connecting the emitter to said first point of potential and impedance means connecting the collector to said second point of potential; means for applying signals to the base of said transistor; a selectively operable shunt path, which includes a single diode which normally does not conduct, connected between the base of said transistor and said first point of potential for when operable providing an additional current path to the applied signal; and normally conducting feedback means including at least one active element connected between the collector of said transistor and said shunt path, said feedback means applying a reverse bias to said diode and simultaneously providing all the current flowing in said shunt path for preventing the conduction of signal current through said shunt path when the signal applied to the base of said transistor is below a given voltage level and said feedback means providing a decreasing amount of current to said shunt path for permitting an increasing amount of signal current in said shunt path when the applied signal increases above said given voltage level.

Claim 3

In combination: first and second terminals for the application therebetween of an operating potential; a transistor having base, emitter, and collector electrodes; impedance means connected between said collector electrode and said first terminal and means connecting said emitter electrode to said second terminal; means for applying input signals to said base electrode, the voltage at said collector electrode being an inverse function of the input signal; a shunt path including solely a single diode in series with a resistor, said shunt path being connected between said base and a point of reference potential; and feedback circuit means, including at least one active element, connected between said collector electrode and the connection of said diode to said resistor; said feedback means being responsive to the voltage at said collector electrode, said voltage being in turn responsive to said input signals; said feedback circuit means in response to input signals of less than a given value applying a reverse bias to said diode and providing all the current flowing in said resistor, and said feedback circuit means in response to input signals of greater than said given value applying a voltage to said diode in a direction to forward bias said diode for enabling a linear increase in the signal current through said shunt path while simultaneously decreasing the portion of the feedback current flowing through said resistor of said shunt path.

Claim 4

In combination: first and second terminals for the application therebetween of an operating potential; a transistor having base, emitter, and collector electrodes; impedance means connected between said collector electrode and said first terminal and means connecting said emitter electrode to said second terminal; means for applying input signals to said base electrode, the voltage at said collector electrode being an inverse function of the input signal; a shunt path including solely a single diode in series with a resistor, said shunt path being connected between said base and a point of reference potential; and feedback circuit means, including at least one active element, connected between said collector electrode and the connection of said diode to said resistor; said feedback means being responsive to the voltage at said collector electrode, said voltage being in turn responsive to said input signals; said feedback circuit means in response to input signals of less than a given value applying a reverse bias to said diode and providing all the current flowing in said resistor, and said feedback circuit means in response to input signals of greater than said given value applying a voltage to said diode in a direction to forward bias said diode for enabling a linear increase in the signal current through said shunt path while simultaneously decreasing the portion of the feedback current flowing through said resistor of said shunt path.

Claim 5

In combination: a transistor having a control electrode, an emitter of charge carriers and a collector of charge carriers; an input circuit connected to said control electrode including an impedance coupled between said control electrode and a point of reference potential; means for applying an input signal to said input circuit; a normally open by-pass circuit connected across said impedance; and normally conducting feedback circuit means connected between said collector of charge carriers and said by-pass circuit; said feedback circuit including at least one active element and being responsive to the voltage at said collector of charge carriers, where said voltage is an inverse function of said input signal; said feedback circuit means providing a curreNt in said by-pass circuit of sufficient magnitude to block the flow of input signal current in the by-pass circuit when the input signal is less than a given value and said feedback circuit providing a decreasing current in said by-pass circuit for linearly closing said by-pass circuit and enabling signal current to pass in said by-pass circuit when the input signal is greater than said given value.

Claim 6

In combination: a transistor having a control electrode, an emitter of charge carriers and a collector of charge carriers; an input circuit connected to said control electrode including an impedance coupled between said control electrode and a point of reference potential; means for applying an input signal to said input circuit; a normally open by-pass circuit connected across said impedance; and normally conducting feedback circuit means connected between said collector of charge carriers and said by-pass circuit; said feedback circuit including at least one active element and being responsive to the voltage at said collector of charge carriers, where said voltage is an inverse function of said input signal; said feedback circuit means providing a curreNt in said by-pass circuit of sufficient magnitude to block the flow of input signal current in the by-pass circuit when the input signal is less than a given value and said feedback circuit providing a decreasing current in said by-pass circuit for linearly closing said by-pass circuit and enabling signal current to pass in said by-pass circuit when the input signal is greater than said given value.

Claim 7

In the combination as set forth in claim 3, said by-pass circuit comprised solely of a diode in series with a resistor, said feedback circuit being connected to the connection of said diode to said resistor and normally maintaining said diode reverse biased, said feedback circuit in response to an input signal of greater than a given value feeding back a voltage to said diode of a sense to forward bias said diode.

Claim 8

In the combination as set forth in claim 4, said active element in said feedback circuit including a second transistor having an emitter-to-base diode, said second transistor being connected at its base to said collector of charge carriers of the first mentioned transistor and being connected at its emitter to the connection between said diode and said resistor.

Claim 9

In the combination as set forth in claim 3, said active element in said feedback circuit including a second transistor, said second transistor having an emitter-to-base diode and being connected at its base to said collector electrode and at its emitter to said by-pass circuit.

Claim 10

The combination comprising: first and second points of operating potential; a first transistor having a base, an emitter, and a collector; means connecting said emitter to said first point of potential; load means connected between said collector and said second point of potential; means for applying signals to the base of said transistor; a clamping circuit connected between the base of said transistor and said first point of potential comprised solely of a diode in series with a resistor, the diode having its anode connected to the base of said transistor and its cathode connected to one end of the resistor, the other end of the resistor being connected to said first point of potential; and feedback means, including a second transistor having its base connected to the collector of said first transistor, its collector connected to said second point of potential, and its emitter connected to the cathode of said diode for providing current to said resistor and maintaining said diode reversed biased for input signals below a given level and providing less circuit to said resistor for enabling a linear increase in the conduction of input signal current through said diode and said resistor for input signals greater than said given value.

Claim 11

The combination comprising: first and second points of operating potential; a first transistor having a base, an emitter, and a collector; means connecting said emitter to said first point of potential; load means connected between said collector and said second point of potential; means for applying signals to the base of said transistor; a clamping circuit connected between the base of said transistor and said first point of potential comprised solely of a diode in series with a resistor, the diode having its anode connected to the base of said transistor and its cathode connected to one end of the resistor, the other end of the resistor being connected to said first point of potential; and feedback means, including a second transistor having its base connected to the collector of said first transistor, its collector connected to said second point of potential, and its emitter connected to the cathode of said diode for providing current to said resistor and maintaining said diode reversed biased for input signals below a given level and providing less circuit to said resistor for enabling a linear increase in the conduction of input signal current through said diode and said resistor for input signals greater than said given value.

Claim 12

The combination as claimed in claim 7 further including a third transistor, said third transistor having its emitter connected to the emitter of said first transistor, and further including means for applying a reference potential to the base of said third transistor, said third transistor being conductive and said first transistor being rendered non-conductive when the signal applied to the base of said first transistor is lower in amplitude than said reference potential and said third transistor being rendered non-conductive and said first transistor being rendered conductive when the signal applied to the base is higher in amplitude than said reference potential.

Claim 13

The combination as claimed in claim 7 wherein said second transistor is a multi-emitter transistor, one emitter of said second transistor being connected to the cathode of said diode and another one of the emitters of said transistors being connected to an output terminal for producing thereat output signals having a first value when the input signal is below a given level and a second value when the input signal is above said given level.

Claim 14

The combination as claimed in claim 7 wherein said means for applying signals to the base of said first transistor includes aN input terminal for the application thereto of signals from a signal source producing signals of relatively large amplitude, and further includes an attenuation and level shifting network connected between said terminal and the base of said first transistor.

Claim 15

The combination as claimed in claim 10, wherein said attenuation and level shifting network includes a first impedance coupled between said input terminal and the base of said first transistor and a second impedance connected between the base of said transistor and said first point of potential.