Amplifier having a constant-current bias circuit

Claim 2

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage including an NPN transistor having a base connected to said first relay terminal and an emitter connected to one end of a first resistor, an output terminal connected to another end of said first resistor and to one end of a second resistor, and a PNP transistor having a base connected to said second relay terminal and an emitter connected to another end of said second resistor; a second PNP transistor having an emitter connected to said first relay terminal, a collector connected to said second relay terminal and a base connected to said another end of the second resistor via a resistor; and a capacitor connected between the base and the emitter of said second PNP transistor, said second PNP transistor being free of direct connection with said output terminal.

Claim 3

An amplifier as in claim 1, further comprising: a constant-current element in electrical connection between a positive power supply and said voltage-controllable constant current bias circuit.

Claim 4

An amplifier as in claim 2, wherein said constant-current element is a P-channel field effect transistor that is serially connected to a resistor.

Claim 5

An amplifier as in claim 2, further comprising: an auxiliary constant-current circuit which includes another transistor operatively connected between said first and second relay terminals.

Claim 6

An amplifier as in claim 4, wherein said another transistor is one of thermo-coupled dual field effect transistor.

Claim 7

An amplifier as in claim 1, wherein a high-cut filter comprises said capacitor and said resistor and has a filter common, further comprising: means for adversely charging said capacitor, interposed between said filter common and a base of said NPN transistor, so as to avoid generating a rush current in said NPN and PNP transistors.

Claim 8

An amplifier as in claim 6, said adversely charging means comprising: a constant voltage element between said filter common and a base of said PNP transistor.

Claim 9

An amplifier as in claim 6, said adversely charging means comprising: a constant voltage element between said filter common and a base of said NPN transistor; and a constant current element between said filter common and a negative power supply.

Claim 10

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage including a first transistor having a gate connected to said first relay terminal and a source connected to one end of a first resistor, an output terminal connected to another end of said first resistor and to one end of a second resistor, and a second transistor having a gate connected to said second relay terminal and a source connected to another end of said second resistor, said second transistor having a polarity opposite to said first transistor; and a voltage-controlled constant current bias circuit connected between said first and second relay terminals and controlling a value of the constant current flowing through said first and second relay terminals in response to a control voltage that is a mean value of a voltage between said one end of the first resistor and said another end of the second resistor via a high-cut filter, said voltage-controlled constant current bias circuit being free of direct connection with said output terminal.

Claim 11

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage including a first transistor having a gate connected to said first relay terminal and a source connected to one end of a first resistor, an output terminal connected to another end of said first resistor and to one end of a second resistor, and a second transistor having a gate connected to said second relay terminal and a source connected to another end of said second resistor, said second transistor having a polarity opposite to said first transistor; and a voltage-controlled constant current bias circuit connected between said first and second relay terminals and controlling a value of the constant current flowing through said first and second relay terminals in response to a control voltage that is a mean value of a voltage between said one end of the first resistor and said another end of the second resistor via a high-cut filter, said voltage-controlled constant current bias circuit being free of direct connection with said output terminal.

Claim 12

An amplifier as in claim 9, wherein said voltage-controlled constant current bias circuit comprises a junction type field effect transistor having a drain connected to one of said first and second relay terminals.

Claim 13

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage including a first transistor having a base connected to said first relay terminal and an emitter connected to one end of a first resistor, an output terminal connected to another end of said first resistor and to one end of a second resistor, and a second transistor having a base connected to said second relay terminal and an emitter connected to another end of said second resistor, said second transistor having a polarity opposite to said first transistor; and a voltage-controlled constant current bias circuit connected between said first and second relay terminals and controlling a value of the constant current flowing through said first and second relay terminals in response to a control voltage that is a mean value of a voltage between said one end of the first resistor and said another end of the second resistor via a high-cut filter, said voltage-controlled constant current bias circuit comprising a junction type field effect transistor having a drain connected to one of said first and second relay terminals.

Claim 14

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage including a first transistor having a base connected to said first relay terminal and an emitter connected to one end of a first resistor, an output terminal connected to another end of said first resistor and to one end of a second resistor, and a second transistor having a base connected to said second relay terminal and an emitter connected to another end of said second resistor, said second transistor having a polarity opposite to said first transistor; and a voltage-controlled constant current bias circuit connected between said first and second relay terminals and controlling a value of the constant current flowing through said first and second relay terminals in response to a control voltage that is a mean value of a voltage between said one end of the first resistor and said another end of the second resistor via a high-cut filter, said voltage-controlled constant current bias circuit comprising a junction type field effect transistor having a drain connected to one of said first and second relay terminals.

Claim 15

An amplifier as in claim 11, further comprising: an on-off controllable constant voltage bias circuit having a third transistor with a collector connected to said first relay terminal and an emitter connected to said second relay terminal, a third resistor connected to said first relay terminal and a base of said third transistor, and a fourth resistor connected to said base of said third transistor; a delay circuit for delaying transmission of a signal for a predetermined period after turning on the power supply; and an isolator for turning off said on-off controllable constant voltage bias circuit in response to receipt of said signal from said delay circuit, said isolator being in electrical connection with both of said third transistor and said delay circuit.

Claim 16

An amplifier as in claim 12, wherein said isolator includes a photo-coupler and a photo-transistor, said photo-coupler having an anode connected to a terminal of said delay circuit and a cathode connected to a ground, said photo-transistor having a collector and an emitter connected to the base and the emitter of said third transistor respectively, said delay circuit including a monostable multivibrator.

Claim 17

An amplifier as in claim 12, wherein said on-off controllable constant voltage bias circuit is in parallel electrical connection with said voltage-controllable current bias circuit.

Claim 18

An amplifier as in claim 12, wherein said voltage-controllable constant current bias circuit includes two transistors, further comprising: a capacitor in electrical connection between two terminals, said two terminals being respectively in electrical connection with bases of said two transistors, said two terminals also being in electrical connection respectively between said first resistor and said first transistor and between said second resistor and said second transistor.

Claim 19

An amplifier as in claim 11, wherein said high-cut filter includes a capacitor, further comprising: means for changing a rate for charging of said capacitor, said changing means including a resistor in parallel between a filter input and a filter output of said high-cut filter, and having a lower resistance than that of said high-cut filter, said changing means including a break contact serially connected to said resistor that has said lower resistance.

Claim 20

An amplifier as in claim 11, further comprising: means for limiting rush emitter currents through said first and second transistors, said limiting means including a first make contact between a positive power supply and a collector of said first transistor of said SEPP output stage, said limiting means also including a second break contact between a negative power supply and a collector of said second transistor of said SEPP output stage.

Claim 21

An amplifier as in claim 11, further comprising: means for limiting rush emitter currents through said first and second transistors, said limiting means also including third and fourth resistors in parallel with said first and second resistors respectively, said third and fourth resistors having a lower resistance than that of said first and second resistors respectively, said limiting means further including a first make contact being in electrical connection with said third resistor, said limiting means including a second make contact being in electrical connection with said fourth resistor.

Claim 22

An amplifier as in claim 11, wherein said high-cut filter includes a capacitor, further comprising: means for adversely charging said capacitor, interposed between a filter common of said high-cut filter and one of said first and second resistors, so as to avoid generating a rush current in said first and second transistors, said adversely charging means including a power source serially connected to said capacitor.

Claim 23

Am amplifier comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage having first and second transistors operatively connected to said first and second relay terminals respectively, first and second resistors operatively connected to said first and second transistors respectively, and an output terminal connected to said first and second resistors; a voltage-controlled constant current bias circuit connected between said first and second relay terminals for controlling a bias current flowing in said first and second resistors via a high-cut filter, said voltage-controllable constant current bias circuit being free of direct connection with said output terminal; said high-cut filter including a capacitor; and means for adversely charging said capacitor, interposed between a common of said high-cut filter and one of said first and second resistors, so as to avoid generating a rush current in said first and second transistors.

Claim 24

Am amplifier comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage having first and second transistors operatively connected to said first and second relay terminals respectively, first and second resistors operatively connected to said first and second transistors respectively, and an output terminal connected to said first and second resistors; a voltage-controlled constant current bias circuit connected between said first and second relay terminals for controlling a bias current flowing in said first and second resistors via a high-cut filter, said voltage-controllable constant current bias circuit being free of direct connection with said output terminal; said high-cut filter including a capacitor; and means for adversely charging said capacitor, interposed between a common of said high-cut filter and one of said first and second resistors, so as to avoid generating a rush current in said first and second transistors.

Claim 25

An amplifier as in claim 20, said adversely charging means comprising: a constant voltage element between said filter common and one of said first and second resistors; and a constant current element between said filter common and one of the relay terminals.

Claim 26

An amplifier as in claim 20, said adversely charging means comprising: a constant voltage element between said filter common and one of said first and second resistors; and a constant current element between said filter common and one of said positive and negative power supplies.

Claim 27

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage having an output terminal and means for providing source and sink current to said output terminal; positive and negative supply terminals in electrical connection with said SEPP output stage; a constant voltage bias circuit connected between said first and second relay terminals for maintaining a voltage constant within said SEPP output stage; and a constant current element connected between the output terminal and at least one of said voltage supply terminals for preventing switching between said source and sink current of said SEPP output stage from arising.

Claim 28

An amplifier, comprising: an input stage having an inverting input terminal and a non-inverting input terminal; a voltage amplifier stage operatively connected to said input stage and having first and second relay terminals; a SEPP output stage having an output terminal and means for providing source and sink current to said output terminal; positive and negative supply terminals in electrical connection with said SEPP output stage; a constant voltage bias circuit connected between said first and second relay terminals for maintaining a voltage constant within said SEPP output stage; and a constant current element connected between the output terminal and at least one of said voltage supply terminals for preventing switching between said source and sink current of said SEPP output stage from arising.

Claim 29

An amplifier as in claim 23, wherein said providing means includes first and second transistors connected to said output terminal, said constant voltage bias circuit maintaining constant a base to base voltage of said first and second transistors.

Claim 30

An amplifier as in claim 23, wherein said providing means includes a first transistor and a diode each connected to said output terminal, said constant voltage bias circuit maintaining constant a base to cathode voltage of said first transistor and said diode.