Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2002-11-05
2003-10-28
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S543000, C323S315000
Reexamination Certificate
active
06639456
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a current mirror in which an input current (I
in
) is nonlinearly converted into a voltage in a current sink, the voltage being used for driving a current source (I
out
) having substantially the same transfer characteristic.
The invention also relates to a method for operating a current mirror.
Current mirrors are circuits or circuit components that, as a response to a current, generate a current of the same intensity.
The prior art uses current mirrors, in particular, in integrated circuits in which data are processed based upon current signals.
A current mirror is, preferably, a circuit or a part of a circuit. It converts an input current into an output current. Preferably, there is a linear relationship between the input current and the output current.
Existing in the prior art is the use of suitably connected transistors as a current sink or as a current source.
Various circuit configurations for current mirrors are described in the book by C. Toumazou, F. J. Lidgey, and D. G. Haigh: “Analogue IC design: the current mode approach”, London 1990.
It is particularly in highly accurate integrated analog circuits that differential signal processing is normally used for reducing the sensitivity of the circuits to interfering influences of the most varied type. While such is achieved by using fully differential operational amplifiers (high CMRR, PSRR, etc.) in circuits that transmit information in the voltage domain, current-mode circuits must use other solutions. In these circuits, quasi-differential current signal processing is frequently used in which two identical but electrically separate circuits are used in parallel. Due to the lack of direct electrical coupling and the possibly large spatial separation of the two signal paths on the chip, the advantages of differential signal processing become relative.
Other prior art embodiments are, in most cases, based upon using differential stages that result in disadvantages with respect to component mismatch and speed and output voltage range of the current mirror.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a current mirror and method for operating a current mirror that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that creates a current mirror that has the highest possible stability, particularly with respect to common-mode signals.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for operating a differential current mirror circuit, including the steps of generating, with devices, at least one copy of a respective one of a positive input current and a negative input current by respectively converting the respective one of the positive input current and the negative input current into a respective voltage, utilizing a respective voltage for respectively driving one current source to generate a copy of a respective one of a positive output current and a negative output current, generating, with a device, one auxiliary current that is one of a multiple and a fraction of each respective one of the positive input current and the negative input current, extracting, with a device, an interference signal by adding the two auxiliary currents, and providing one device each to generate the positive output current and the negative output current by subtracting the interference signal from a respective one of a copy of the positive input current and a copy of the negative input current.
With the objects of the invention in view, there is also provided a method for operating a differential current mirror circuit, including the steps of generating, with first devices, at least one copy of a respective one of a positive input current and a negative input current by respectively converting the respective one of the positive input current and the negative input current into a respective voltage, generating, with a second device, one auxiliary current that is one of a multiple and a fraction of each respective one of the positive input current and the negative input current, extracting, with a third device, an interference signal by adding the two auxiliary currents, and utilizing a respective voltage for respectively driving one current source to generate a copy of a respective one of a positive output current and a negative output current by providing one device each to generate the positive output current and the negative output current by subtracting the interference signal from a respective one of a copy of the positive input current and a copy of the negative input current.
In accordance with another mode of the invention, there is provided the step of generating the two auxiliary currents as one half of the respective one of the positive input current and the negative input current.
In accordance with a further mode of the invention, the device for generating the positive output current and the negative output current has at least one complementary current mirror.
In accordance with an added mode of the invention, there is provided the step of generating a multiple of the copy of the respective one of the positive input current and the negative input current respectively as the positive output current and as the negative output current.
In accordance with an additional mode of the invention, there is provided the step of generating a number of copies of the respective one of the positive input current and the negative input current.
With the objects of the invention in view, there is also provided a differential current mirror circuit, including devices generating at least one copy each of a respective one of a positive input current and a negative input current by respectively converting the respective one of the positive input current and the negative input current into a respective voltage, a respective current source connected to the devices, the respective voltage driving each current source to generate a copy of a respective one of a positive output current and a negative output current, a device connected to a respective one of the current sources and to the devices and respectively generating one auxiliary current that is one of a multiple and a fraction of the respective one of the positive input current and the negative input current, a device connected to a respective one of the current sources and to the devices and extracting an interference signal by adding the two auxiliary currents, and devices each generating the positive output current and the negative output current by subtracting the interference signal from a respective one of a copy of the positive input current and the negative input current.
With the objects of the invention in view, there is also provided a differential current mirror circuit, including first means for generating at least one copy each of a respective one of a positive input current and a negative input current by respectively converting the respective one of the positive input current and the negative input current into a respective voltage, a respective current source connected to the devices, the respective voltage driving each current source to generate a copy of a respective one of a positive output current and a negative output current, second means for respectively generating one auxiliary current that is one of a multiple and a fraction of the respective one of the positive input current and the negative input current, the second generating means connected to a respective one of the current sources and to the devices, means for extracting an interference signal by adding the two auxiliary currents, the extracting means connected to a respective one of the current sources and to the first means, and third means for respectively generating the positive output current and the negative output current by subtracting the interference signal from a respective one of a copy of the positive input current and the negative input current.
In accordance with yet
Cunningham Terry D.
Greenberg Laurence A.
Infineon - Technologies AG
Mayback Gregory L.
Stemer Werner H.
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