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US 5,510,755 AGranted
Temperature stable voltage-controlled electronic capacitance for an oscillator
AssigneeSGS-Thomson Microelectronics S.A.
InventorsMarc Kodrnja, Vincent Dufossez
Life of this patent
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Abstract
A voltage-controlled capacitor includes a multiplier, having an output which serves as terminals of the controlled capacitor. The output voltage of the multiplier is applied to a reference capacitor. A signal in phase with the current in the reference capacitor is applied at one input of the multiplier, the other input of the multiplier receiving a signal determining the value of the controlled capacitor.
Claims21
A voltage-controlled capacitor including:
- two parallel differential pairs of transistors cross-controlled by a first differential signal, respective output branches of said two differential pairs constituting terminals of the voltage controlled capacitor;
- two biasing transistors that determine respective bias currents of the two differential pairs of transistors as a function of a second differential signal;
- two reference capacitors;
- means for applying a voltage present at each of the controlled capacitor terminals to a respective one of the two reference capacitors;
- means for providing, as said second differential signal, a current in each one of the two reference capacitors;
- a compensation capacitor;
- and
- two compensation transistors having first main electrodes connected together by the compensation capacitor and being connected in parallel between their first main electrode, their second main electrodes and their control electrodes, the two compensation transistors being coupled to the differential pairs of transistors and to the biasing transistors.
5 more elements
A voltage-controlled capacitor including:
- a multiplier having two differential transistor pairs cross-controlled by a differential control signal, and first and second biasing transistors, each biasing transistor being coupled to a respective differential transistor pair, each biasing transistor having a control lead for receiving a differential reference signal, the multiplier providing an output voltage signal derived from a product of the differential control signal and the differential reference signal;
- first and second capacitors, each capacitor having a first terminal and a second terminal;
- means for providing to the first terminal of the first and second capacitors a respective first and second voltage signal, the first and second voltage signals being derived from the output voltage signal of the multiplier;
- means for providing a first signal in phase with a current in the first capacitor to the control lead of the first biasing transistor;
- means for providing a second signal in phase with a current in the second capacitor to the control lead of the second biasing transistor;
- and
- wherein the output voltage signal of the multiplier simulates electrical characteristics of a capacitor having a capacitance that is derived at least in part from the differential control signal and from the first and second voltage signal across the first and second capacitor.
4 more elements
An oscillator assembly comprising:
- an oscillator;
- and
- a voltage controlled capacitor coupled to the oscillator and including:
- a multiplier having two differential transistor pairs cross-controlled by a differential control signal, and first and second biasing transistors, each biasing transistor being coupled to a respective differential transistor pair, each biasing transistor having a control lead for receiving a differential reference signal, the multiplier providing an output voltage signal derived from a product of the differential control signal and the differential reference signal;
- first and second capacitors, each capacitor having a first terminal and a second terminal;
- means for providing to the first terminal of the first and second capacitors a respective first and a second voltage signal, the first and second voltage signals being derived from the output voltage signal of the multiplier;
- means for providing a first signal in phase with a current in the first capacitor to the control lead of the first biasing transistor;
- means for providing a second signal in phase with a current in the second capacitor to the control lead of the second biasing transistor;
- and
- wherein the output voltage signal of the multiplier simulates electrical characteristics of a capacitor having a capacitance that is derived at least in part from the differential control signal and from the first and second voltage signal across the first and second capacitor.
7 more elements
A voltage controlled capacitance having a first terminal and a second terminal, the voltage controlled capacitance comprising:
- a multiplier circuit having first and second pairs of differential voltage input terminals and first and second differential current output terminals, wherein the first and second differential voltage input terminals receive respective first and second differential voltage input signals, wherein a differential current output signal of the multiplier circuit is substantially proportional to a product of the first and second differential voltage input signals, wherein the first terminal of the voltage controlled capacitance is coupled to the first differential current output terminal and the second terminal of the voltage controlled capacitance is connected to the second current output terminal;
- first and second resistors, the first resistor being connected between a supply voltage and the first differential current output terminal, the second resistor being connected between the supply voltage and the second differential current output terminal;
- first and second linearizing circuits, the first linearizing circuit being connected to a first differential voltage input terminal of the second pair of differential voltage input terminals, the second linearizing circuit being connected to a second differential voltage input terminal of the second pair of differential voltage input terminals;
- and
- first and second reference capacitors, the first reference capacitor being coupled between the supply voltage and the first differential voltage input terminal of the second pair of differential voltage input terminals, the second reference capacitor being coupled between the supply voltage and the second differential voltage input terminal of the second pair of differential voltage input.
2 more elements
Dependencies are inferred from the claim text.