Differential transconductor with reduced temperature dependence
AssigneeSGS-Thomson Microelectronics S.A.
InventorsRoberto Alini, Francesco Rezzi, Gianfranco Vai, Marco Gregori
Life of this patent
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Abstract
An integrated circuit transconductor stage which suppresses the dependence on temperature and production process variables of a differential transconductor stage. A negative feedback relation is used, where the output of the transconductor stage is connected to an additional current generator (which is referenced to a precision external resistor), to a capacitor, and also to the gate of a PMOS transistor which sources current to a polarization stage, which in turn sources current to the transconductor stage, or to multiple transconductor stages.
Claims24
An integrated circuit, comprising:
- a differential transconductor stage, operatively connected to receive an input voltage, and at least one bias current, and configured to source an output current which is linearly dependent on variations in said input voltage, and which is also dependent on said bias current;
- a polarization circuit operatively connected to source said bias current to said transconductor stage;
- a programmable current source, comprising an external precision resistor which is substantially temperature-independent, operatively connected to provide an additional current component, at said current output of said transconductor stage, which is generally proportional to said input voltage divided by the value of said precision resistor;
- a capacitor operatively connected between ground and said current output of said transconductor stage;
- and
- a P-channel field-effect transistor connected to source current to said polarization circuit, and connected to be controlled by the voltage of said current output of said transconductor stage;
- whereby temperature-dependent current variations in said current output of said transconductor stage are compensated by variations in the current passed by said P-channel field-effect transistor.
An integrated circuit, comprising:
- a differential transconductor stage, operatively connected to receive an input voltage, and at least one bias current, and configured to provide an output current which is linearly dependent on variations in said input voltage, and which is also dependent on said bias current;
- a polarization circuit operatively connected to receive a first bias current, and to provide one or more corresponding second bias currents to said transconductor stage;
- a current source operatively connected to receive a substantially constant temperature- and process-independent current, opposite in sign to said output current of said transconductor stage, from said output of said transconductor stage;
- a feedback transistor connected to provide said first bias current to said polarization circuit, and connected to be controlled by the voltage of said output of said transconductor stage;
- whereby temperature-dependent current variations in said current output of said transconductor stage are compensated by variations in the current passed by said feedback transistor.
An integrated circuit, comprising:
- first and second transconductor stages, each operatively connected to receive a respective input voltage, and at least one bias current, and configured to provide an output current which is linearly dependent on variations in said input voltage, and which is also dependent on said bias current;
- a polarization circuit operatively connected to receive a first bias current, and accordingly to provide one or more second bias signals to each of said transconductor stages;
- a current source operatively connected to receive a substantially constant temperature- and process-independent current, opposite in sign to said output current of said transconductor stage, from said output of said first transconductor stage;
- a feedback transistor connected to provide said first bias current to said polarization circuit, and connected to be controlled by the voltage of said output of said first transconductor stage;
- whereby temperature-dependent current variations in said current output of said transconductor stage are compensated by variations in the current passed by said feedback transistor.
A method for operating a transconductor, comprising the steps of:
- (a.) providing a substantially constant voltage to the input of a first transconductor stage, and to a substantially temperature-independent resistance;
- (b.) dynamically adjusting bias current to said first transconductor stage in a feedback relation such that the output of said first transconductor stage is made equal to an additional current, derived from said substantially constant voltage and from said substantially temperature-independent resistance, to the output of said first transconductor stage;
- (c.) providing bias current to one or more second transconductor stages, corresponding to said bias current provided to said first transconductor stage;
- (d.) providing respective voltage input signals to said second transconductor stages, and generating respective corresponding current output signals in each of said second transconductor stages accordingly.
A circuit device for suppressing the dependence on temperature and production process variables of the transconductance of a differential transconductor stage incorporating a polarization circuit, comprising a negative feedback loop closed across an output of the stage and an input of the polarization circuit, and including a current generator, capacitor, and at least a transistor.
A circuit device for suppressing the dependence on temperature and production process variables of the transconductance of a plurality of differential transconductor stages being supplied in parallel from a polarization circuit, comprising a negative feedback loop closed across an output of one of said stages and an input of the polarization circuit and including a current generator, capacitor, and at least a transistor.
Dependencies are inferred from the claim text.