Semiconductor amplifier protection

Claim 2

An amplifier protection circuit comprising: an amplifier transistor and a protection transistor each having base, emitter and collector electrodes constructed on the same semi-conductor wafer, means providing a source of direct voltage substantially independent of signal variations equal to the threshold voltage of conductivity of the base emitter junction of said protection transistor at an upper operating limit semiconductor temperature, means connecting said source of direct voltage between the base and emitter electrodes of said protection transistor to effect base emitter junction conduction in said protection transistor for semiconductor temperatures higher than said limit temperature, an input signal circuit including a pair of terminals coupled to the base and emitter electrodes of said amplifier transistor, and means connecting the collector and emitter electrodes of said protection transistor between said pair of terminals whereby said protection transistor provides a low impedance bypass for input signals for semiconductor temperatures higher than said limit temperature.

Claim 3

An amplifier protection circuit according to claim 1 and further comprising: means coupled in series with the emitter-collector current path of said amplifier transistor for sensing said current, and means for coupling said current sensing means to said base-emitter junction of said protection transistor for rendering said protection transistor responsive to predetermined conditions of temperature and current in said amplifier transistor.

Claim 4

An amplifier protection circuit according to claim 2 and further comprising: means coupled between the collector and emitter electrodes of said amplifier transistor for sensing voltage across said electrodes, and means for coupling said voltage sensing means to said base-emitter junction of said protection transistor for rendering said protection transistor responsive to predetermined conditions of current, voltage and temperature of said amplifier transistor.

Claim 5

An amplifier protection circuit comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter-collector current path of said amplifier transistor, means providing a source of direct voltage bias substantially independent of signal variations equal to the threshold voltage of conductivity of the base emitter junction of said protection transistor at an upper operating limit temperature, means connecting the current sampling means and said source of direct voltage bias in series between the base and emitter electrodes of said protection transistor for rendering said protection transistor responsive to predetermined combinations of operating temperature and amplifier current, an input signal circuit including a pair of terminals coupled to the base and emitter electrodes of said amplifier transistor, and means connecting the collector to emitter current path of said protection transistor between said pair of terminals whereby said protection transistor provides a low impedance signal bypass across said input circuit for excess amplifier current as a function of said protection transistor temperature.

Claim 6

An amplifier protection circuit comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter-collector current path of said amplifier transistor, means providing a source of direct voltage bias substantially independent of signal variations equal to the threshold voltage of conductivity of the base emitter junction of said protection transistor at an upper operating limit temperature, means connecting the current sampling means and said source of direct voltage bias in series between the base and emitter electrodes of said protection transistor for rendering said protection transistor responsive to predetermined combinations of operating temperature and amplifier current, an input signal circuit including a pair of terminals coupled to the base and emitter electrodes of said amplifier transistor, and means connecting the collector to emitter current path of said protection transistor between said pair of terminals whereby said protection transistor provides a low impedance signal bypass across said input circuit for excess amplifier current as a function of said protection transistor temperature.

Claim 7

An amplifier protection circuit as described in claim 4 wherein a voltage divider means is connected between the collector and emitter electrodes of said amplifier transistor for providing a fraction of the emitter-collector voltage of said amplifier transistor across a portion of said voltage divider, and said means connecting the current sampling means and said source of relatively fixed voltage in series also connects the portion of the voltage divider in series between the base and emitter electrodes of said protection transistor, whereby said protection transistor is also responsive to said amplifier transistor emitter-collector voltage.

Claim 8

An amplifier protection circuit as described in claim 4 wherein; the amplifier transistor and said protection transistor are constructed on a single semiconductor wafer.

Claim 9

An amplifier protection circuit comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter to collector current path of said amplifier transistor, voltage divider means connected between said current sampling means and a source of relatively fixed voltage for providing a bias voltage across a portion of said voltage divider means substantially equal to the threshold conduction voltage of the base-emitter junction of said protection transistor at an upper operating limit temperature, means connecting said current sampling means and said portion of said voltage divider means in series between the base and emitter electrodes of said protection transistor, and means connecting the collector to emitter path of said protection transistor between the base and emitter electrodes of said amplifier transistor.

Claim 10

An amplifier protection circuit comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter to collector current path of said amplifier transistor, voltage divider means connected between said current sampling means and a source of relatively fixed voltage for providing a bias voltage across a portion of said voltage divider means substantially equal to the threshold conduction voltage of the base-emitter junction of said protection transistor at an upper operating limit temperature, means connecting said current sampling means and said portion of said voltage divider means in series between the base and emitter electrodes of said protection transistor, and means connecting the collector to emitter path of said protection transistor between the base and emitter electrodes of said amplifier transistor.

Claim 11

An amplifier protection circuit as described in claim 7 wherein said amplifier transistor, said protection transistor, said current sampling means, and said voltage divider means are constructed on a single semiconductor wafer as an integrated circuit.

Claim 12

An amplifier and protection circuit therefore comprising: an amplifier transistor having base-emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter to collector current path of said amplifier transistor, first voltage divider means connected between the collector and emitter electrodes of said amplifier transistor, second voltage divider means connected between a point on said first voltage divider means and a source of relatively fixed voltage, the relative parameters of said First and second voltage dividers being such that a relatively fixed voltage is developed across said second voltage divider means and a portion of said fixed voltage is substantially equal to the threshold conduction voltage of the base-emitter junction of said protection transistor at an upper operating limit temperature, means connecting said current sampling means, a portion of said first voltage divider means, and a portion of said second voltage divier means corresponding to said threshold voltage in series between the base and emitter electrodes of said protection transistor, and means connecting the collector to emitter path of said protection transistor between the base and emitter electrodes of said amplifier transistor.

Claim 13

An amplifier and protection circuit therefore comprising: an amplifier transistor having base-emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; a current sampling means coupled in series with the emitter to collector current path of said amplifier transistor, first voltage divider means connected between the collector and emitter electrodes of said amplifier transistor, second voltage divider means connected between a point on said first voltage divider means and a source of relatively fixed voltage, the relative parameters of said First and second voltage dividers being such that a relatively fixed voltage is developed across said second voltage divider means and a portion of said fixed voltage is substantially equal to the threshold conduction voltage of the base-emitter junction of said protection transistor at an upper operating limit temperature, means connecting said current sampling means, a portion of said first voltage divider means, and a portion of said second voltage divier means corresponding to said threshold voltage in series between the base and emitter electrodes of said protection transistor, and means connecting the collector to emitter path of said protection transistor between the base and emitter electrodes of said amplifier transistor.

Claim 14

An amplifier and protection circuit as described in claim 9 wherein a portion of said first voltage divider means is common to a portion of said second voltage divider means, the relative parameters of said first and second voltage dividers being such that the relatively fixed voltage is developed across the portion of said first voltage divider means common to said second voltage divider means.

Claim 15

An amplifier and protection circuit therefore comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; current sampling means connected in series with the emitter electrode of said amplifier transistor; first voltage divider means connected between the collector and emitter electrodes of said amplifier transistor; second voltage divider means connected across a source of relatively fixed voltage so that a relatively fixed voltage is developed across said second voltage divider means; means including the current sampling means connecting the collector-to-emitter path of said protection transistor to the base and emitter electrodes of said amplifier transistor; and means connecting said current sampling means, a portion of said first voltage divider means, and a portion of said second voltage divider means in series between the base and emitter electrodes of said protection transistor, said portion of said second voltage divider means providing to said protection transistor a bias voltage substantially equal to the threshold conduction voltage of said protection transistor at an upper operating limit temperature.

Claim 16

An amplifier and protection circuit therefore comprising: an amplifier transistor having base, emitter and collector electrodes; a protection transistor having base, emitter and collector electrodes; current sampling means connected in series with the emitter electrode of said amplifier transistor; first voltage divider means connected between the collector and emitter electrodes of said amplifier transistor; second voltage divider means connected across a source of relatively fixed voltage so that a relatively fixed voltage is developed across said second voltage divider means; means including the current sampling means connecting the collector-to-emitter path of said protection transistor to the base and emitter electrodes of said amplifier transistor; and means connecting said current sampling means, a portion of said first voltage divider means, and a portion of said second voltage divider means in series between the base and emitter electrodes of said protection transistor, said portion of said second voltage divider means providing to said protection transistor a bias voltage substantially equal to the threshold conduction voltage of said protection transistor at an upper operating limit temperature.