The present invention concerns an electronic system including at least a first electronic device with semiconductor components comprising at least an input terminal, an output terminal, a high supply terminal brought to a high potential VDD, and a low supply terminal brought to a low potential VSS, defining a supply voltage VDD−VSS, said system allowing the electric power consumption of certain conventional electric circuits to be lowered when said system is associated therewith.
Indeed, electronic circuits with semiconductor components have in particular the peculiarity of having different operating conditions as a function of the supply voltage that is applied to them. The user of such circuits generally wishes to be able to have a sufficiently broad range of use in terms of supply voltage to prevent, in particular, the risk of abrupt variations in the supply voltage. Consequently, the common fields of use of electronic circuits with semiconductor components are often precisely delimited within the low supply voltage region, as regards the ranges corresponding to stable operating conditions.
The electronics field is constantly searching for solutions for lowering the power consumption of circuits, particularly through a drop in the minimum permissible supply voltage for said circuits to operate in a stable manner. A solution that is currently used and regularly improved consists in modifying the physical features of the semiconductor components, such as their geometry, the nature of the doping agents used or their quantity, such that the value of their threshold voltage is lowered.
It can thus easily be deduced from analysing
However, the solution consisting in modifying the physical features of the semiconductors often has the drawback of making the corresponding manufacturing process much more complex and thus more expensive than conventional processes.
The main object of the present invention is to improve the power consumption of electronic circuits with semiconductor components of the prior art while overcoming the aforementioned drawbacks of the prior art.
The invention therefore concerns an electronic system of the aforementioned type, characterised in that said electronic device has a transfer function H1 the graphic representation of which, as a function of said supply voltage, includes three successive fields, the first field ranging from the low values of VDD−VSS to a value VT, called the threshold value of the semiconductor components, said field corresponding to a high and substantially constant value of H1, the second field ranging from VT to a value VC2, corresponding to a sharply sloping decrease in H1 and the third field extending beyond VC2, corresponding to a low and substantially constant value of H1.
More precisely, a main object of the present invention is to provide an electronic system of the type described hereinbefore and whose output terminal at least is capable of being connected to a second electronic device with semiconductor components also powered by voltage VDD−VSS and having a transfer function H2 the graphic representation of which, as a function of the supply voltage, includes three successive ranges, the first range ranging from low values of VDD−VSS to a value VT, called the threshold voltage of the semiconductor components, said first range corresponding to a low and substantially constant value of H2, the second range ranging from VT to a value VC1, corresponding to a sharply sloping increase in H2 and the third range extending beyond VC1, corresponding to a high and substantially constant value of H2, characterised in that said first electronic device has a transfer function H1 that varies as a function of the supply voltage VDD−VSS, such that the electronic system has a transfer function H3 that varies as a function of the supply voltage VDD−VSS so as to be substantially constant from a value of supply voltage VC3 lower than VC1.
In order to reach this result, the first electronic device is preferably made such that it includes at least a capacitive type voltage division stage connected, on the one hand, to a first of said two supply terminals and, on the other hand, to said input terminal, said voltage division stage including at least one transistor made in SOI technology including a gate connected, in particular, to said output terminal of said first electronic device, a source and a drain connected to each other and connected to said first supply terminal, said first device also including means for polarising said transistor connected, on the one hand, to the second of said two supply terminals, and on the other hand, to the gate of said transistor.
This type of system is particularly well adapted when the second device described hereinbefore includes at least one electronic circuit taken from the group including amplifiers and oscillators with semiconductor components, insofar as these electronic circuits generally have transfer function curves of the type of that shown in FIG. 2.
Of course, those skilled in the art will know how to implement the system according to the invention, without any particular difficulty, to lower the power consumption of any semiconductor circuit other than those mentioned hereinbefore and having a feature of the type described hereinbefore.
In a preferred embodiment, the first device further includes a second output terminal, a second capacitive type voltage division stage connected, on the one hand, to the second of said two supply terminals and, on the other hand, to said input terminal, the second voltage division stage comprising at least a second SOI type transistor whose type of doping agent is different to that of the transistor of said first stage and including a gate connected, in particular, to said second output terminal, a source and a drain connected to each other and connected to said second supply terminal, said second device also including means for polarising the second transistor connected, on the one hand to the first of said two supply terminals, and on the other hand, to the gate of said second transistor.
In this case, the input terminal of the second electronic device can be connected either to the first or the second of the two outputs of the first electronic device. The electronic system according to the invention may also include a third electronic device including an electronic circuit taken from the same group as that of the electronic circuit of the second device and connected to the other of the outputs of the first electronic device.
In a preferred variant of the preceding embodiment, an output stage can be added between the output terminals of the second and third devices and the output terminal of the complete system, said output stage assuring the recombination of the signals respectively delivered by said two output terminals.
One will consider, by way of illustrative example, a particular case of the different embodiments which have just been described wherein the electronic circuit employed in the second device is a conventional amplifier as shown in FIG. 1. As a result of its features, the electronic system according to the invention thus allows a signal to be amplified with a constant gain while lowering the necessary difference between the high and low supply potentials, i.e. the supply voltage of the circuit, thus reducing the power consumption of said circuit. Indeed, in order to operate in amplification mode, the transistors present in the amplification stages have to be biased with a voltage more or less equal to a particular value, called the threshold voltage. This threshold voltage generally varies from one transistor to another as a function of their respective geometrical and physical parameters. The transfer curve of a transistor used in an amlification mode, as a function of its polarisation voltage, has a transition zone around the threshold voltage. Consequently, an amplification stage with transistors has a gain that varies when the circuit supply voltage varies around the threshold voltage. When the value of the circuit supply voltage sufficiently exceeds the value of the threshold voltage, the gain procured by the amplification stage becomes constant. Typically, the constant gain amplifiers of the prior art are thus powered with supply voltages considerably far from the corresponding threshold voltage in order to avoid the aforementioned problems.
The electronic system according to the present invention includes, in a first electronic device, a voltage divider circuit including capacitive elements of variable capacitance for taking account of and even compensating for the variation in the amplification gain of the electronic circuit used in the second device as a function of the supply voltage, in the transition zone of the transistors used. More precisely, when the system supply voltage increases from the value of the threshold voltage, the gain of an amplification circuit increases significantly. At the same time, the value of the variable capacitance also increases, in the same proportions, such that the outgoing signal from the voltage divider stage entering the amplification circuit has a lower amplitude. Thus, one can obtain a global gain for the system that does not vary with its supply voltage, by a simple compensation effect between the voltage divider and amplification circuits.
The system according to the present invention becomes particularly advantageous when the capacitive elements are made in the form of transistors, in particular in Silicon on Insulator (SOI) type technology. Indeed, the capacitance of an SOI transistor varies significantly as a function of the polarisation voltage that is applied thereto. When said polarisation voltage is less than or equal to threshold voltage VT of the transistor, its capacitance is low while it increases quickly, when said polarisation voltage increases from VT to reach a higher constant value beyond a certain value of the polarisation voltage. Thus, it is possible to adjust the physical features of these capacitive elements with variable capacitance such that their behaviour, as a function of the supply voltage applied to the system, compensates for the transitory behaviour of the elements involved in the amplification circuit. It is thus possible, in accordance with the present invention, to supply the system with a lower voltage than in the case of the amplification circuits of the prior art, while keeping a constant value for the amplification gain.
The invention will be better understood using the following description of an example embodiment made with reference to the annexed drawings, in which:
a shows an electric diagram of a conventional capacitive type voltage divider bridge including two capacitors;
b shows an electric diagram of a voltage divider stage according to the present invention including, particularly, the transistor shown in
As described hereinbefore, the present invention brings a solution combining a conventional electronic circuit, like for example amplification circuit 100 shown in
The basic principle on which the present invention rests consists in limiting the amplitude of the incoming signal into the amplification circuit as a function of the supply voltage and the corresponding increase in amplification gain H2. Thus, for two different supply voltage values, taken in portion 202 of
In practice, in order to carry out this amplitude limitation of the incoming signal in the amplification circuit, one can for example use a capacitive type voltage divider bridge as an additional electronic device. In such case, one of the capacitive elements forming said divider bridge can have a variable capacitance, and in particular this may depend directly on the value chosen for the circuit supply voltage.
In a preferred embodiment of the invention, a transistor is used, occupying less space on an integrated circuit than a conventional capacitor, to perform the function of said variable capacitance element. In fact, a transistor whose source and drain are short-circuited behave like a capacitor whose capacitance fluctuates as a function of the polarisation voltage that is applied thereto. Generally, this latter feature is perceived as a drawback within the electronic chip manufacturing field, insofar as it delimits a range of use for the transistor as a capacitor, in terms of supply voltage.
The curve corresponding to the behaviour of the capacitance of a transistor, as a function of the polarisation voltage that is applied thereto, has the same general shape as the curve shown in FIG. 2. In this case, portion 201 of said curve would correspond to a low value Cb of the capacitance, portion 202 would correspond to the transition zone and portion 203 would correspond to a high value Ch of the capacitance.
Generally, the ratio Ch/Cb rarely reaches 2 for a transistor made in CMOS technology (Complementary Metal Oxide Semiconductor) whereas it can reach values as high as 15 for a transistor made in SOI technology (Silicon On Insulator). These two types of transistors can be employed to implement the present invention, but it is clear than a transistor made in SOI technology offers greater flexibility of use.
When this transistor 300 is used as a capacitor, source 305 and drain 306 are short-circuited thus forming a first terminal of the capacitor whereas gate 308 forms the second terminal of said capacitor. It is clear, upon observing
Of course, the description of the transistor which precedes also applies to a P type transistor having a similar structure to that visible in
a shows an electric diagram of a simple voltage divider bridge, of the capacitive type, including two conventional capacitors with respective capacitances C1 and C2, hereinafter respectively referenced capacitor C1 and capacitor C2. Capacitor C1 is connected, on the one hand, to an input terminal through which an input signal Ve is applied, and on the other hand, to a first terminal of capacitor C2 whose second terminal is connected to a fixed potential VSS. An output terminal is disposed between the two capacitors through which the output signal VS is recuperated. By a simple calculation, one can determine the transfer function k of this circuit which has a value:
k=VS/Ve=C1/(C1+C2).
b shows an electric diagram of a similar voltage divider bridge to that of
H1=VS/Ve=C1/(C1+CT1).
As was mentioned hereinbefore, when the potential difference VDD−VSS varies, the value of CT1 varies and thus the value of H1 also varies.
It is possible to define more or less precisely the operating features of the semiconductor components, such as transistor Q1 or amplification circuit 100, from the physical features of these components, adjusted during their manufacture. Consequently, it is also possible to define these physical features such that the threshold voltages VT are substantially the same for transistor Q1 and for the components of amplification circuit 100 and such that VC1 is substantially equal to VC2. Thus, portions 202 of the curve shown in
This peculiarity allows a general structure to be defined for electronic system 600 according to the present invention, shown in FIG. 6. Said electronic system 600 includes at least one input terminal 601 capable of receiving an input signal Vin, an output terminal 602 delivering an output signal Vout, a high supply terminal brought to a potential VDD and a low supply terminal brought to a potential VSS. The system further includes a first electronic device, referenced D1, connected in particular to input terminal 601 of system 600 and to said supply terminals. Device D1 includes, in particular, an electronic circuit of the type having a similar feature to that shown in
Electronic system 600 can also include a third electronic device, designated D3, connected to a second output terminal 604 of first electronic device D1 and to the supply terminals of system 600. Device D3 includes an electronic circuit of the same type as that described hereinbefore in relation to second electronic device D2 and device D1 preferably includes an additional electronic circuit also having a similar feature to that shown in FIG. 5. In this case, devices D2 and D3 respectively include at least one output terminal, respectively designated by the reference numerals 605 and 606, defining two output terminals for system 600. It is however possible to add an output stage 607, possibly connected to the supply terminals of system 600, for carrying out the combination of the signals originating from output terminals 605 and 606, so as to define a single output signal Vout.
The general structure of the electronic system shown in
The input of sub-circuit B1 is connected to a first terminal 702 of a capacitor C1 whose second terminal 703 is connected to gate 704 of an N type transistor Q1, and preferably similar to that shown in FIG. 3. Gate 704 of transistor Q1 is also connected to polarisation means 705, like those shown in
The structure of sub-circuit B2 has a certain symmetry with respect to that of sub-circuit B1. In fact, input 701 of sub-circuit B2 is connected to a first terminal 715 of a capacitor C2 the second terminal 716 of which is connected to the gate 717 of a P type transistor Q2 that is preferably symmetrical with respect to transistor Q1. Gate 717 of transistor Q2 is also connected to polarisation means 705 like transistor Q1. The source and the drain of transistor Q2 are short-circuited and connected to high potential VDD of the power source. Capacitor C2 and transistor Q2, which here performs the function of a capacitor, thus form a capacitive voltage divider bridge whose output 718, located between said second terminal 716 of said capacitor and the gate 717 of the transistor, is connected to a first input 719 of a similar amplification stage 720 to that used in sub-circuit B1. Output 721 of said amplification stage is connected to second input 722 so as to form a feedback loop and is further connected to gate 723 of a fourth N type transistor Q′2. The source 724 of transistor Q′2 is connected to low potential VSS of the power source whereas its drain 725 is connected to the output terminal 714 of the amplification system.
It should be noted that the respective amplification stages 708 and 720 are here shown as follower circuits for reasons of simplicity, but of course, those skilled in the art will have no difficulty in adapting these stages so as to obtain amplification stages with predefined gains.
An input signal Vin of amplification system 700 according to the invention is divided into two components S1 and S2 respectively simultaneously processed by said two sub-circuits B1 and B2. Since supply voltage VDD−VSS is fixed for example at 4VT, VT being the threshold voltage preferably common to all the transistors employed in the amplification circuit, the components S1 and S2 are attenuated by passing into the respective voltage divider bridges. The corresponding fractions of components S1 and S2 are then respectively injected into the first inputs of the respective amplification stages to be amplified therein. The corresponding amplified fractions of said components S1 and S2 are then combined through, respectively, transistors Q′1 and Q′2 to give, at the output of amplification system 700, a single output signal Vout corresponding simply to the amplified input signal with an amplification gain H3.
According to the preceding description of curve 2, it will be realised that if one now fixes the supply voltage of a supply circuit in accordance with the prior art at 2VT, the operating point of the system is located in transition region 202 and the amplification gain of the system is no longer the same except for a supply voltage of 4VT.
However, owing to the features of the amplification system according to the invention, a supply voltage even slightly less than 2VT is sufficient to obtain an amplification gain H3 substantially equal to the gain obtained with a supply voltage fixed at 4VT, for example.
This result is apparent from curves a and b shown in
As was mentioned hereinbefore, it can be seen in curve a of
Consequently, it can be deduced that the advantage in terms of supply voltage for the amplification system according to the invention with respect to the circuits of the prior art has a value of ΔV=VC1−VC3.
Concretely, this advantage means a saving of the order of 0.5 to 1 volt on the supply voltage for the amplification system according to the present invention, which makes it particularly well suited for applications requiring low power consumption, such as in portable apparatuses.
The preceding description relates to a preferred embodiment of the invention and should in no way be considered as limiting, as regards for example the nature of the elements used to amplify the signal, the type of technology employed to integrate the components or the components employed at the output of the amplification stages for combining the signals originating from the two sub-circuits B1 and B2 to obtain a single output signal Vout.
It is of course possible to take advantage of the teaching of the present invention to perform asymmetrical amplification of an input signal by choosing for example to fix the respective gains of the two amplification stages at different values.
The possible applications of the electronic system according to the invention are numerous and those skilled in the art will of course know how to make any necessary adaptations to integrate it into a more general system, such as in an oscillator circuit for example. One could particularly envisage the use of such a system to make an oscillator for regulating the working of an electromechanical watch powered by a microgenerator, for example of the type disclosed in Patent document Nos. CH 597 636, EP 0 239 820 or EP 0 679 968.
Number | Date | Country | Kind |
---|---|---|---|
220901 | Dec 2001 | CH | national |
Number | Name | Date | Kind |
---|---|---|---|
3816811 | Cmelik | Jun 1974 | A |
3887881 | Hoffmann | Jun 1975 | A |
3937001 | Berney | Feb 1976 | A |
3956714 | Luscher | May 1976 | A |
4023112 | Duncker et al. | May 1977 | A |
5796296 | Krzentz | Aug 1998 | A |
5991177 | Kaczkowski | Nov 1999 | A |
6040744 | Sakurai et al. | Mar 2000 | A |
6172378 | Hull et al. | Jan 2001 | B1 |
6515903 | Le et al. | Feb 2003 | B1 |
6518814 | Majid et al. | Feb 2003 | B1 |
Number | Date | Country |
---|---|---|
443507 | Aug 1991 | EP |
Number | Date | Country | |
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20030102853 A1 | Jun 2003 | US |