Current mirror amplifier

Abstract

A current mirror amplifier circuit with an input current path and an output current path is further provided with a sensing means responsive to the cessation of current flow in the output current path such that the cessation of current flow in the output current path causes the current flow in the input current path to be discontinued.

What is claimed is: 
     
       1. In combination: a current mirror amplifier having an input current path between an input terminal and a common terminal, and an output current path between an output terminal and said common terminal; and   means responsive to the cessation of current flow in said output current path for discontinuing the flow of current through said input current path.   
     
     
       2. A combination as set forth in claim 1 wherein said means responsive to the cessation of current flow in said output current path for discontinuing the flow of current through said input path includes means for sensing at least a portion of the potential appearing across said output current path and responding to that portion of the potential falling below a prescribed value to discontinue the flow of current through said input current path. 
     
     
       3. A current mirror amplifier comprising: input, output and common terminals;   first and second transistors each having a first electrode and each having a principal conduction path between second and third electrodes, the conductivity of which path is controlled by the potential between its first and second electrodes, the first electrodes of said first and said second transistors being connected to each other, the second electrodes of said first and said second transistors being connected to said common terminal, and the third electrodes of said first and said second transistors being connected respectively to said input terminal and to said output terminal;   a degenerative feedback connection between the third and first electrodes of said first transistor; and   means responsive to the cessation of current flow through the principal conduction path of said second transistor for discontinuing said degenerative feedback connection.   
     
     
       4. In a current mirror amplifier with a. first and second transistors, each having a first electrode and each having a principal conduction path between second and third electrodes, the conductivity of which path is controlled by the potential between its first and second electrodes, their second electrodes being connected to a common reference potential;   b. a degenerative feedback connection between the third electrode of said first transistor and its first electrode for applying a potential between its second and first electrodes to condition it to conduct input current applied to its principal conduction path;   c. means for applying the same potential to the first electrode of said second transistor as to the first electrode of said first transistor, for implementing an output current flow through the principal conduction path of said second transistor proportionally responsive to any input current flow through the principal conduction path of said first transistor;   d. a load; and   e. means for connecting and disconnecting said load to the principal conduction path of said second transistor to receive said output current; the improvement comprising:     f. an analog switch connected to control the flow of current in the principal conduction path of said first transistor; and   g. means responsive to the connection of said load to render said analog switch conductive and responsive to the disconnection of said load to render said analog switch non-conductive.   
     
     
       5. The improvement set forth in claim 4 wherein said analog switch is interposed in said degenerative feedback connection. 
     
     
       6. In a current mirror amplifier with input, output and common terminals, said input and common terminals for receiving an input current;   first and second transistors of a first conductivity type, each having a conduction path;   a direct coupled degenerative feedback connection between the collector and base electrodes of said first transistor, for applying an emitter-to-base potential to said first transistor responsive to said input current;   means for applying an emitter-to-base potential to said second transistor similar to that applied to said first transistor, for causing the respective collector current of said first and said second transistors to be in substantially fixed proportion to each other, the improvement comprising:   means responsive to the absence of output current flow through said output terminal for discontinuing said direct-coupled degenerative feedback connection.   
     
     
       7. The improvement set forth in claim 6 wherein said direct coupled degenerative feedback connection between the collector and base electrodes of said first transistor, said means for applying an emitter-to-base potential to said second transistor similar to that applied to said first transistor, and said means responsive to the absence of output current flow through said output terminal for interrupting said direct-coupled degenerative feedback connection together comprise: third and fourth transistors of a second conductivity type and a fifth transistor of said first conductivity type, said second conductivity type being complementary to said first conductivity type, each of said third and fourth and fifth transistors having base and emitter and collector electrodes, the emitter electrode of said third transistor being connected to said output terminal, the collector electrodes of said third and said fifth transistors being connected respectively to the base electrode of said fifth transistor and to the base electrode of said third transistor, the emitter electrode of said fifth transistor being connected to the base electrodes of said first and said second transistors, the base electrode of said fourth transistor having the collector electrode of said first transistor having the collector electrode of said first transistor connected thereto, the emitter electrode of said fourth transistor being connected to the base electrode of said fifth transistor, and the collector electrode of said fourth transistor referred to said common terminal.   
     
     
       8. The improvement set forth in claim 6 wherein said direct coupled degenerative feedback connection between the collector and base electrodes of said first transistor, said means for applying an emitter-to-base potential of said second transistor similar to that applied to said first transistor, and said means responsive to the absence of output current flow through said output terminal for interrupting said direct-coupled degenerative feedback connection together comprise: a third transistor being of the same conductivity type as said first and said second transistors, being a field-effect transistor, having a gate electrode to which the collector of the first transistor is connected, having a source electrode connected to an interconnection between the base electrodes of said first and said second transistors, and having a drain electrode connected to said output terminal.   
     
     
       9. In a current mirror amplifier with input, output and common terminals,   first and second transistors having respective emitter electrodes connected to said common terminal, having respective collector electrodes respectively connected to said input terminal and to said output terminal, having respective base electrodes;   a direct coupled degenerative feedback connection between the collector and base electrodes of said first transistor for applying an emitter-to-base potential to said first transistor responsive to said input current;   means for applying an emitter-to-base potential to said second transistor similar to that applied to said first transistor, for causing the respective collector currents of said first and said second transistors to be in substantially fixed proportion to each other, the improvement comprising:   means responsive to the absence of substantial potential appearing between said common and said output terminals for discontinuing said direct-coupled degenerative feedback connection.   
     
     
       10. The improvement set forth in claim 9 wherein said direct-coupled degenerative feedback connection between the collector and base electrodes of said first transistor, said means for applying an emitter-to-base potential to said first transistor similar to that applied to said first transistor, and said means responsive to the absence of substantial potential appearing between said common and said output terminals for interrupting said direct-coupled degenerative feedback connection together comprise: a third transistor being of the same conductivity type as said first and said second transistors, being a field-effect transistor, having a gate electrode to which said output terminal is connected, having a source electrode connected to an interconnection between the base electrodes of said first and said second transistors, and having a drain electrode to which the collector electrode of said first transistor is connected.   
     
     
       11. A current mirror amplifier comprising: input, and output and common terminals;   first and second and third transistors of a first conductivity type and a fourth transistor of a second conductivity type complementary to said first conductivity type, each of said transistors having base and emitter and collector electrodes, the emitter electrodes of said first and said second transistors each being connected to said common terminal, the collector electrodes of said first and said second transistors being connected respectively to said input terminal and to said output terminal;   means connecting said third and said fourth transistors in a regenerative latch circuit including the coupling of the collector electrode of each to the base electrode of the other;   means for coupling said output terminal to the emitter electrode of said fourth transistor;   means for coupling the emitter electrode of said third transistor to the base electrodes of said first and said second transistors; and   unilaterally conductive means connecting said first transistor collector electrode to said third transistor base electrode and poled for conducting a portion of the collector current of said first transistor.   
     
     
       12. A current mirror amplifier as set forth in claim 11 wherein said unilaterally conductive means comprises the base-emitter junction of a fifth common-collector amplifier transistor of said second conductivity type. 
     
     
       13. A current mirror amplifier as set forth in claim 12 wherein the common-collector amplifier action of at least one further transistor of said first conductivity type provides said means for coupling the emitter electrode of said third transistor to the base electrodes of said first and said second transistor. 
     
     
       14. A current mirror amplifier as set forth in claim 11 wherein the common-collector amplifier action of at least one further transistor of said first conductivity type provides said means for coupling the emitter electrode of said third transistor to the base electrodes of said first and said second transistors. 
     
     
       15. A current mirror amplifier comprising: input, common and output terminals;   first, second, third, fourth and fifth transistors, each having base and emitter and collector electrodes, said first and second and third and fourth transistors being of a first conductivity type and said fifth transistor being of a second conductivity type complementary to said first conductivity type, the emitter electrodes of said first and said second transistors being connected to said common terminal, the collector electrodes of said first and third transistors being connected respectively to said input terminal and to said output terminal, the collector electrode of said second transistor being connected to the emitter electrode of said third transistor, and the emitter electrode of said third transistor similarly connected to the respective base electrodes of said first and said second transistors;   means connecting said fourth and said fifth transistors in a regenerative latch circuit including the coupling of the collector electrode of each to the base electrode of the other;   means for coupling the output terminal to the emitter electrode of said fifth transistor;   means for coupling the emitter electrode of said fourth transistor to the base electrode of said third transistor; and   unilaterally conductive means connecting said first transistor collector electrode to said fourth transistor base electrode and poled for conducting a portion of the collector current of said first transistor.   
     
     
       16. A current mirror amplifier as set forth in claim 15 wherein said unilaterally conductive means comprises the base-emitter junction of a sixth common-collector amplifier transistor of said second conductivity type. 
     
     
       17. A current mirror amplifier as set forth in claim 16 wherein common-collector amplifier action of at least one further transistor of said first conductivity type provides said means for coupling the emitter electrode of said fourth transistor to the base electrode of said third transistor. 
     
     
       18. A current mirror amplifier as set forth in claim 15 wherein common-collector amplifier action of at least one further transistor of said first conductivity type provides said means for coupling the emitter electrode of said fourth transistor to the base electrode of said third transistor. 
     
     
       19. A current mirror amplifier comprising: input, output and common terminals;   first and second junction transistors having respective collector electrodes respectively connected to said input and said output terminals, having respective emitter electrodes each connected to said common terminal, and having respective base electrodes; and   a field-effect transistor having a gate electrode connected to said input terminal and having a source-to-drain path connecting the collector electrode of said second junction transistor to the base electrodes of said first and said second junction transistors.   
     
     
       20. A current mirror amplifier comprising: input, output and common terminals;   first and second junction transistors having respective collector electrodes respectively connected to said input and said output terminals, having respective emitter electrodes each connected to said common terminal; and having respective base electrodes; and   a field-effect transistor having a gate electrode connected to said output terminal and having a source-to-drain path connecting the collector electrode of said first junction transistor to the base electrodes of said first and said second transistors. .Iadd. 21. A current amplifier comprising:   input, output and common terminals;   first and second transistors each having a respective first electrode and each having a respective principal conduction path between respective second and third electrodes, the conductivity of which path is controlled by the potential between its first and second electrodes, the second electrodes of said first and said second transistors being connected to said common terminal, and the third electrodes of said first and said second transistors being connected respectively to said input terminal and to said output terminal;   means for generating an electric control signal; and   analog switch means responsive to said electric control signal for providing a selective connection between said input terminal and a common connection of the first electrodes of said first and second transistors. .Iaddend..Iadd. 22. A current amplifier as set forth in claim 21 wherein said analog switch means includes a third transistor of similar conductivity type to said first and second transistors, and fourth and fifth transistors of opposite conductivity type, each of said third, fourth and fifth transistors having a respective first electrode and a respective principal conduction path between respective second and third electrodes, the conductivity of which path is controlled by the potential between its first and second electrodes, the second and third electrodes of said third transistor being respectively connected to said common connection of the first electrodes of said first and second transistors and to the first electrode of said fourth transistor, the second electrode of said fourth transistor having said control signal applied thereto, and the third electrode of said fourth transistor being connected to an interconnection between the first electrode of said third transistor and the second electrode of said fifth transistor, the first electrode of said fifth transistor having said input terminal connected thereto, and the third electrode of said fifth transistor being connected to condition said fifth transistor for operation as an emitter follower whenever said analog switch means provides said selective connection. .Iaddend..Iadd. 23. A current amplifier as set forth in claim 21 wherein said analog switch means includes a third transistor being of similar conductivity type to said first and second transistors, having a first electrode and having a principal conduction path between second and third electrodes, the conductivity of which path is controlled by the potential between its first and second electrodes, the first electrode of said third transistor having said input terminal connected thereto, the second electrode of said third transistor being connected to said common connection of the first electrodes of said first and second transistors, and the third electrode of said third transistor having said control signal applied thereto. .Iaddend..Iadd. 24. A current amplifier as set forth in claim 21 wherein said analog switch means includes a third transistor which is of enhancement-mode field effect type and of a conductivity type similar to that of said first and second transistors, has a gate electrode to which said input terminal is connected, has a source electrode connected to said common connection of the first electrodes of said first and second transistors, and has a drain electrode to which said control signal is applied. .Iaddend..Iadd. 25. A current amplifier as set forth in claim 21 wherein said analog switch means includes a third transistor which is of field effect type, has a drain electrode to which said input terminal is connected, has a source electrode connected to said common connection of the first electrodes of said first and second transistors, and has a gate electrode to which said control signal is applied. .Iaddend. .Iadd. 26. A current amplifier comprising:   input, output, and common terminals;   first and second transistors of the same conductivity type, each having a respective first electrode and having a respective principal conduction path between respective second and third electrodes thereof, the conductivity of which path is controlled by the potential between its first and second electrodes, the second electrode of said first transistor being connected to said common terminal, the second electrode of said second transistor being connected to the first electrode of said first transistor, and the third electrodes of said first and second transistors being respectively connected to said input terminal and to said output terminal;   resistive means connecting the second electrode of said second transistor to said common terminal;   means for generating a control signal; and   analog switch means responsive to said electric control signal for providing a selective connection between said input terminal and the first electrode of said second transistor. .Iaddend.