Current mirror circuit and method for providing zero temperature coefficient trimmable current ratios

Claim 2

Circuit for providing an output current that is proportional to an applied input current and having first and second current paths, comprising: current supply means for supplying a thermal current to the first current path, said thermal current having the form of (kT/qR)1n K, where k is Boltzmann's constant, q is the charge of an electron, R is a resistance of a given resistivity and temperature coefficient, T is absolute temperature and K is a constant; diode means coupled in the first current path through which substantially all of said thermal current flows; a first transistor the base-emitter junction of which is coupled in a parallel conduction path with respect to said diode means and the collector-emitter junction being coupled in the second current path such that the output current flows therethrough; and trimmable resistive means having substantially the same temperature coefficient as said resistance R for adjusting the ratio of the thermal current to said output current with said adjusted ratio being both constant and temperature independent.

Claim 3

The circuit of claim 1 wherein said diode means is a second transistor having a collector, an emitter and a base with said collector and base being shorted to said base of said first transistor and receiving said thermal current.

Claim 4

The circuit of claim 2 wherein said trimmable resistive means is a resistor connected between said emitter of said first transistor and a terminal to which is supplied ground reference potential.

Claim 5

The circuit of claim 2 wherein said trimmable resistive means is a resistor connected between said emitter of said second transistor and a terminal to which is supplied a ground reference potential.

Claim 6

The circuit of claim 2 wherein said trimmable resistive means includes; a first resistor connected between said emitter of said first transistor and a terminal to which is supplied ground reference potential; and a second resistor connected between said emitter of said second transistor and said terminal.

Claim 7

A current mirror circuit for providing an output current the magnitude of which is proportional to the magnitude of a supplied reference current, comprising: current source means for supplying a thermal reference current, said thermal reference current having the form of (kT/qR)1n K, where k is Boltzmann's constant, q is the charge of an electron, R is a resistance of a given resistivity and temperature coefficient, T is absolute temperature and K is a constant; diode means which is forward biased by said thermal reference current; a first transistor having a control electrode coupled to said diode means and first and second electrodes, said transistor providing said output current at said second electrode thereof; and trimmable resistive means having substantially the same temperature coefficient as said resistance R coupled in series between said first electrode of said first transistor and a common terminal for adjusting the magnitude of the output current for a given thermal reference current wherein the adjusted ratio of the two currents is substantially temperature independent.

Claim 8

A current mirror circuit for providing an output current the magnitude of which is proportional to the magnitude of a supplied reference current, comprising: current source means for supplying a thermal reference current, said thermal reference current having the form of (kT/qR)1n K, where k is Boltzmann's constant, q is the charge of an electron, R is a resistance of a given resistivity and temperature coefficient, T is absolute temperature and K is a constant; diode means which is forward biased by said thermal reference current; a first transistor having a control electrode coupled to said diode means and first and second electrodes, said transistor providing said output current at said second electrode thereof; and trimmable resistive means having substantially the same temperature coefficient as said resistance R coupled in series between said first electrode of said first transistor and a common terminal for adjusting the magnitude of the output current for a given thermal reference current wherein the adjusted ratio of the two currents is substantially temperature independent.

Claim 9

The current mirror circuit of claim 6 wherein said diode means is a second transistor having first, second and control electrodes, said control and second electrodes being interconnected to said control electrode of said first transistor and receiving said thermal reference current.

Claim 10

The current mirror circuit of claim 7 including resistive means coupled in series between said first electrode of said second transistor and said common terminal.

Claim 13

A current mirror arrangement including at least first and second current circuit paths, comprising: current supply means for providing a thermal current at an output thereof of the form, (kT/qR) 1n K, where k is Boltzmann's constant, T is absolute temperature, q is the charge of an electron, R is the resistance of a given resistivity and temperature coefficient and K is a constant; the first current circuit path including semiconductor diode means coupled to said current supply means through which substantially all of said thermal current flows; the second current circuit path including the collector-emitter conduction path of a first transistor the base of which is coupled to said current supply means; and

Claim 14

A current mirror arrangement including at least first and second current circuit paths, comprising: current supply means for providing a thermal current at an output thereof of the form, (kT/qR) 1n K, where k is Boltzmann's constant, T is absolute temperature, q is the charge of an electron, R is the resistance of a given resistivity and temperature coefficient and K is a constant; the first current circuit path including semiconductor diode means coupled to said current supply means through which substantially all of said thermal current flows; the second current circuit path including the collector-emitter conduction path of a first transistor the base of which is coupled to said current supply means; and

Claim 15

trimmable resistive means having the same temperature coefficient as said resistance for adjusting the ratio of the currents in the first and second current circuit paths with respect to one another wherein said adjusted ratio is both constant and temperature independent.

Claim 16

trimmable resistive means having the same temperature coefficient as said resistance for adjusting the ratio of the currents in the first and second current circuit paths with respect to one another wherein said adjusted ratio is both constant and temperature independent.

Claim 17

The current mirror of claim 10 wherein said trimmable resistive means includes: a first resistor coupled between said diode means and a common terminal, the resistance of said first resistor being trimmable and having substantially the same temperature coefficient as said resistance of given resistivity; and a second resistor coupled between the emitter of said first transistor and said common terminal, the resistance of said second resistor being trimmable and having substantially the same temperature coefficient as said first resistor.

Claim 18

The current mirror of claim 10 wherein: said trimmable resistive means includes a resistor coupled between the emitter of said first transistor and a common terminal; and said semiconductor diode means is coupled between said output of said current supply means and said common terminal.

Claim 19

The current mirror of claim 10 wherein said trimmable resistive means includes: a resistor coupled between said semiconductor diode means and a common terminal, the resistance of said resistor being trimmable; and means for connecting the emitter of said first transistor to said common terminal.