Abstract:
An electronic system with semiconductor components allows electronic circuits with conventional semiconductor components to be used, having minimal supply voltages to guarantee stable operation, lowering said minimum supply voltages. The range of supply voltages of such a circuit for which operation is stable can be extended towards low values by the effect of mutual compensation of the respective behaviors of said semiconductor components in their respective transition regions.

Description:
BACKGROUND OF THE INVENTION 
   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 V DD , and a low supply terminal brought to a low potential V SS , defining a supply voltage V DD −V SS , 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. 
     FIG. 1  shows, by way of non-limiting example, a common electronic circuit, more precisely a common type of amplification circuit  100  (gain equal to 1 here) and including, in particular, semiconductor elements (not shown). Amplification circuit  100  includes, in particular, two input terminals  101  and  102 , an output terminal  103  and two supply terminals i.e. one high terminal  104  and one low terminal  105 . Input terminal  101  is powered by an input signal V 1  whereas input terminal  102  is connected to output terminal  103  thus forming a feedback loop. Further, output terminal  103  is brought to an output potential V 2 . High supply terminal  104  is connected to a high potential V DD  whereas low supply terminal  105  is connected to a low potential V SS . 
     FIG. 2  shows the behaviour of the amplification circuit or stage shown in  FIG. 1  when the difference of potentials V DD −V SS  is varied by applying a potential V 1  of constant amplitude to input  101 . The ordinate scale on the curve of  FIG. 2  corresponds to the ratio V 2 /V 1  of the output voltage over the input voltage, in other words to the gain or the transfer function H 2  of the amplification stage shown in FIG.  1 . It will thus be noted that gain H 2 , whose value is negligible for low values of the difference of potentials V DD −V SS ,  201 , increases rapidly from the moment when the potential difference V DD −V SS  reaches a noted value V T  which is the threshold voltage of the semiconductor components used in the construction of the amplification stage. The curve then defines a portion  202  constituting a transition zone in the behaviour of amplification stage  100 . A last portion  203  will also be noted on the curve of gain H 2  shown in  FIG. 2 , located after value V C1 , in the zone where the value of potential difference V DD −V SS  is considerably greater than V T . In this last portion  203 , the value of amplification gain H 2  remains substantially constant. Generally, V C1  corresponds to a value higher than 2 V T  or 2.5 V T . 
   It can thus easily be deduced from analysing  FIG. 2  that an amplification stage such as that shown in  FIG. 1  can be used as an amplifier with a constant gain H 2 , for different supply voltage values, provided that the latter are sufficiently higher than the threshold voltage of the semiconductor components used to be at the level of portion  203 . 
   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. 
   SUMMARY OF THE INVENTION 
   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 H 1  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 V DD −V SS  to a value V T , called the threshold value of the semiconductor components, said field corresponding to a high and substantially constant value of H 1 , the second field ranging from V T  to a value V C2 , corresponding to a sharply sloping decrease in H 1  and the third field extending beyond V C2 , corresponding to a low and substantially constant value of H 1 . 
   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 V DD −V SS  and having a transfer function H 2  the graphic representation of which, as a function of the supply voltage, includes three successive ranges, the first range ranging from low values of V DD −V SS  to a value V T , called the threshold voltage of the semiconductor components, said first range corresponding to a low and substantially constant value of H 2 , the second range ranging from V T  to a value V C1 , corresponding to a sharply sloping increase in H 2  and the third range extending beyond V C1 , corresponding to a high and substantially constant value of H 2 , characterised in that said first electronic device has a transfer function H 1  that varies as a function of the supply voltage V DD −V SS , such that the electronic system has a transfer function H 3  that varies as a function of the supply voltage V DD −V SS  so as to be substantially constant from a value of supply voltage V C3  lower than V C1 . 
   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 V T  of the transistor, its capacitance is low while it increases quickly, when said polarisation voltage increases from V T  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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood using the following description of an example embodiment made with reference to the annexed drawings, in which: 
       FIG. 1  shows a simple amplification stage, powered by a supply voltage V DD −V SS  as known from the prior art; 
       FIG. 2  shows the curve describing the behaviour of the amplification factor H 2  of the amplification stage shown in  FIG. 1 , as a function of the supply voltage that is applied thereto; 
       FIG. 3  shows a cross-section of an embodiment example of an SOI transistor according to the present invention; 
       FIG. 4   a  shows an electric diagram of a conventional capacitive type voltage divider bridge including two capacitors; 
       FIG. 4   b  shows an electric diagram of a voltage divider stage according to the present invention including, particularly, the transistor shown in  FIG. 3 ; 
       FIG. 5  shows the ratio of the output voltage over the input voltage of the voltage divider stage shown in  FIG. 4 , as a function of the supply voltage applied to the circuit; 
       FIG. 6  shows a schematic diagram defining the general structure of the electronic system according to the present invention; 
       FIG. 7  shows the electric diagram of a simple embodiment example of the electronic system according to the present invention, and 
       FIG. 8  shows the behaviour of the transfer function of the electronic system shown in  FIG. 7  as a function of the supply voltage applied to said system and compared to the behaviour of an electronic circuit of the prior art. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As described hereinbefore, the present invention brings a solution combining a conventional electronic circuit, like for example amplification circuit  100  shown in  FIG. 1 , with an additional electronic device such that portion  203  of  FIG. 2  starts from a value V C3  (shown in  FIG. 8 ) lower than V C1 , or lower than 2V T . Thus, for a given amplification circuit and amplification gain H 2 , the user of the complete system according to the present invention can use a lower supply potential difference than in the case of the amplification circuits of the prior art. This feature advantageously allows less power to be consumed for a given amplification gain than with a circuit of the prior art. 
   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 H 2 . Thus, for two different supply voltage values, taken in portion  202  of  FIG. 2 , the gain of amplification stage H 2  is fixed at two different values and the amplitude of the signal to be amplified is consequently attenuated differently in these two cases in accordance with the invention, such that the overall gain H 3  of the complete amplification system is the same for said two supply voltage values. 
   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. 
     FIG. 3  shows a cross-section of an embodiment example of such an SOI type transistor  300 , as disclosed in U.S. Pat. No. 6,172,378, to which the interested reader may refer to obtain further details. 
     FIG. 3  shows the simplified conventional structure of a chip made in SOI technology, namely a substrate  301 , on which an insulated layer  302 , made for example of silicon dioxide, is arranged, and on which is arranged a silicon layer  303  used for integrating the components. Trenches  304  filled with insulator are disposed around a region of said chip in which said transistor  300  is integrated. Silicon layer  303  is doped with different doping agents depending on the location. Two metal contacts are disposed at the surface of said region, in contact with N+ doped regions of the second silicon layer, defining source  305  and drain  306  of transistor  300 . The free portions of the second silicon layer are covered with a thin layer of oxide  307 , on which an N doped silicon layer is deposited between the source and the drain, so as to form gate  308  of the transistor. 
   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  FIG. 3 , that as a function of the voltage applied to said terminals of said capacitor, the physical properties of the channel (here of the P-type, located in layer  303 ) of the transistor are modified, causing a modification in the corresponding capacitance value. 
   Of course, the description of the transistor which precedes also applies to a P type transistor having a similar structure to that visible in  FIG. 3  with only slight differences, particularly as regards the doping regions. 
     FIG. 4   a  shows an electric diagram of a simple voltage divider bridge, of the capacitive type, including two conventional capacitors with respective capacitances C 1  and C 2 , hereinafter respectively referenced capacitor C 1  and capacitor C 2 . Capacitor C 1  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 C 2  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=V   S   /V   e   =C   1 /( C   1   +C   2 ). 
     FIG. 4   b  shows an electric diagram of a similar voltage divider bridge to that of  FIG. 4   a , wherein capacitor C 2  has been replaced by a transistor Q 1 , so as to form a capacitor with a capacitance C T1 , like that shown in FIG.  3 . It will be noted that an additional part appears in the diagram of  FIG. 4   b , corresponding to a conventional polarisation circuit of the transistor, which will not be described in more detail in the present Application. For this circuit, the transfer function H 1  becomes:
   H   1 = V   S   /V   e   =C   1 /( C   1   +C   T1 ). 
   As was mentioned hereinbefore, when the potential difference V DD −V SS  varies, the value of C T1  varies and thus the value of H 1  also varies. 
     FIG. 5  shows the curve giving the behaviour of H 1  as a function of V DD −V SS  for a fixed input voltage value V e . It will be noted that for the values of V DD −V SS  lower than V T , which corresponds to a non conducting state for transistor Q 1 , the transfer function H 1  of the voltage divider bridge is constant and equal to value h 1 . It can also be noted that when the value of V DD −V SS  increases from V T  to a value referenced V C2 , which corresponds to the transition region of transistor Q 1 , the value of H 1  gradually decreases until it is again constant and equal to a value h 2  after V C2 , when the transistor is in the steady-state conditions. Three portions can thus be distinguished in the curve of  FIG. 5 , portion  501  corresponding to the values of V DD −V SS  lower than V T , portion  502  corresponding to the values of V DD −V SS  comprised between V T  and V C2  and portion  503  corresponding to the values of V DD −V SS  higher than V C2 . 
   It is possible to define more or less precisely the operating features of the semiconductor components, such as transistor Q 1  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 V T  are substantially the same for transistor Q 1  and for the components of amplification circuit  100  and such that V C1  is substantially equal to V C2 . Thus, portions  202  of the curve shown in  FIG. 2 and 502  of the curve shown in  FIG. 5  are superposed and the progressive increase in the amplification circuit gain is at least partially compensated for by the progressive decrease in amplitude of the outgoing signal from the voltage divider circuit. In this way, the transfer function of the complete system, including in succession, said voltage divider circuit and the amplification circuit, has a substantially constant value over a large part of the range of values of V DD −V SS  corresponding to the transition region conditions of the semiconductor components. It is also easier to adjust the capacitance value of the capacitor with a high level of precision such that the compensation is almost perfect at least in the last part of the portion of curve  202  located beside portion  203 . 
   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 V in , an output terminal  602  delivering an output signal V out , a high supply terminal brought to a potential V DD  and a low supply terminal brought to a potential V SS . The system further includes a first electronic device, referenced D 1 , connected in particular to input terminal  601  of system  600  and to said supply terminals. Device D 1  includes, in particular, an electronic circuit of the type having a similar feature to that shown in  FIG. 5 , thus for example, at least one voltage divider stage like that shown in  FIG. 4   b . Device D 1  further includes an output terminal  603  connected to a second electronic device, designated by the reference D 2  and connected to the supply terminals of system  600 . Device D 2  includes, in particular, an electronic circuit of the type having a similar feature to that shown in  FIG. 2 , thus for example, an amplification stage like that shown in  FIG. 1 , or even a conventional type of oscillator (not shown). 
   Electronic system  600  can also include a third electronic device, designated D 3 , connected to a second output terminal  604  of first electronic device D 1  and to the supply terminals of system  600 . Device D 3  includes an electronic circuit of the same type as that described hereinbefore in relation to second electronic device D 2  and device D 1  preferably includes an additional electronic circuit also having a similar feature to that shown in FIG.  5 . In this case, devices D 2  and D 3  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 V out . 
   The general structure of the electronic system shown in  FIG. 6  has been advantageously used to design the electronic system  700  ensuring constant gain amplification in accordance with the embodiment of the invention shown in FIG.  7 . It is important to note that the embodiment example shown in  FIG. 7  has deliberately been chosen for its simplicity so as to show the essential features of the present invention. In the embodiment described here solely by way of illustration, the constant gain amplification system includes two sub-circuits designated B 1  and B 2  both having main input  701  of the system as their input. 
   The input of sub-circuit B 1  is connected to a first terminal  702  of a capacitor C 1  whose second terminal  703  is connected to gate  704  of an N type transistor Q 1 , and preferably similar to that shown in FIG.  3 . Gate  704  of transistor Q 1  is also connected to polarisation means  705 , like those shown in  FIG. 4   b  for example. The source and the drain of transistor Q 1  are short-circuited and connected to low potential V SS  of a power source (not shown). Capacitor C 1  and transistor Q 1  which here performs the function of a capacitor, thus form a capacitive voltage divider bridge whose output  706 , located between said second terminal  703  of said capacitor and the gate  704  of transistor Q 1  is connected to a first input  707  of an amplification stage  708  like the one shown in FIG.  1 . The output  709  of said amplification stage  708  is connected to second input  710  so as to form a feedback loop and it is further connected to gate  711  of a second P type transistor Q′ 1 . The source  712  of transistor Q′ 1  is connected to high potential V DD  of the power source whereas its drain  713  is connected to the output terminal  714  of the amplification system. 
   The structure of sub-circuit B 2  has a certain symmetry with respect to that of sub-circuit B 1 . In fact, input  701  of sub-circuit B 2  is connected to a first terminal  715  of a capacitor C 2  the second terminal  716  of which is connected to the gate  717  of a P type transistor Q 2  that is preferably symmetrical with respect to transistor Q 1 . Gate  717  of transistor Q 2  is also connected to polarisation means  705  like transistor Q 1 . The source and the drain of transistor Q 2  are short-circuited and connected to high potential V DD  of the power source. Capacitor C 2  and transistor Q 2 , 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 B 1 . 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 V SS  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 V in  of amplification system  700  according to the invention is divided into two components S 1  and S 2  respectively simultaneously processed by said two sub-circuits B 1  and B 2 . Since supply voltage V DD −V SS  is fixed for example at 4V T , V T  being the threshold voltage preferably common to all the transistors employed in the amplification circuit, the components S 1  and S 2  are attenuated by passing into the respective voltage divider bridges. The corresponding fractions of components S 1  and S 2  are then respectively injected into the first inputs of the respective amplification stages to be amplified therein. The corresponding amplified fractions of said components S 1  and S 2  are then combined through, respectively, transistors Q′ 1  and Q′ 2  to give, at the output of amplification system  700 , a single output signal V out  corresponding simply to the amplified input signal with an amplification gain H 3 . 
   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 2V T , 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 4V T . 
   However, owing to the features of the amplification system according to the invention, a supply voltage even slightly less than 2V T  is sufficient to obtain an amplification gain H 3  substantially equal to the gain obtained with a supply voltage fixed at 4V T , for example. 
   This result is apparent from curves a and b shown in  FIG. 8  showing the behaviour of amplification gain H 3  as a function of the variation in the supply voltage of the amplification system, respectively according to the prior art and according to the present invention. 
   As was mentioned hereinbefore, it can be seen in curve a of  FIG. 8  that the amplification gain of the circuit according to the prior art becomes constant from a value of V DD −V SS  greater than V C1  which is greater than 2V T  here. Further, it will be noted on curve b of  FIG. 8  that the amplification gain according to the present invention becomes constant from a value of V DD −V SS  greater than V C3  which is less than 2V T  here. 
   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=V C1 −V C3 . 
   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 B 1  and B 2  to obtain a single output signal V out . 
   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.