EP1324170A1 - Circuit à transconductance sensiblement constante - Google Patents
Circuit à transconductance sensiblement constante Download PDFInfo
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- EP1324170A1 EP1324170A1 EP02080252A EP02080252A EP1324170A1 EP 1324170 A1 EP1324170 A1 EP 1324170A1 EP 02080252 A EP02080252 A EP 02080252A EP 02080252 A EP02080252 A EP 02080252A EP 1324170 A1 EP1324170 A1 EP 1324170A1
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- Prior art keywords
- circuit
- transconductance
- mos transistor
- circuit according
- mos
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
- G05F3/02—Regulating voltage or current
- G05F3/08—Regulating voltage or current wherein the variable is dc
- G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
- G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
- G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
- G05F3/26—Current mirrors
- G05F3/262—Current mirrors using field-effect transistors only
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/561—Voltage to current converters
Definitions
- the present invention relates to a circuit in MOS technology with substantially constant transconductance, in particular, a transconductance circuit with at least one transconductance cell mounted between two supply terminals including a MOS transistor.
- transconductance circuits often called voltage-current converter are widely used in analog integrated circuits in particular in assemblies integrators to make, for example filters, oscillators, delay circuits.
- Such transconductance circuits may include active circuits and resistors R in polysilicon or diffused and their transconductance Gm is a function of the ratio 1 / R. But the value of resistance R varies with temperature, which makes the value of unstable transconductance. In addition, the value of the resistance depends on the manufacturing process. The tolerance on the resistance value is of the order of plus or minus 15 to 20% and this is affects transconductance.
- the transconductance circuits produced in bipolar or MOS technology have a transconductance Gm which is proportional to I / V T or to I / 2Vgt respectively, I being the current delivered by the transconductance circuit, V T the threshold voltage and Vgt the voltage saturation grid ('GATE OVERDRIVE VOLTAGE', in English) of a MOS transistor.
- the transconductance Gm varies in particular like the current and this one is not constant and depends on the one hand on the temperature and on the other hand of the manufacturing process.
- this transconductance Gm is substantially constant, because on its value depends the circuit time constant.
- these integrating circuits include at least one circuit with transconductance Gm and at least one integration capacitor C connected to the output of the transconductance circuit and their time constant T is proportional to the ratio C / Gm. he is important that the time constant T be as constant as possible in a large number of applications. We also try to make this time constant known with precision and therefore be as insensitive as possible to the circuit manufacturing process integrator.
- the servo circuit requires a reference clock, counters, phase detection circuit or loop circuit phase lock for measurement and a network of resistors and capacitors for the correction. This control circuit significantly increases the cost of integrating circuit, its energy consumption as well as its size.
- the present invention aims precisely to simply realize a circuit transconductance in MOS technology whose transconductance is substantially constant.
- the transconductance depends among other things of the mobility ⁇ of the majority carriers (electrons or holes depending on the type of MOS transistor) in the channel of the MOS transistor and this quantity varies greatly with temperature.
- the idea to make the transconductance substantially constant is to compensate for the variations thermal mobility ⁇ of the majority carriers.
- the present invention proposes a transconductance circuit with at least one transconductance cell mounted between two supply terminals including at minus one MOS transistor. It includes means for biasing the MOS transistor of the cell with a bias current whose variation as a function of temperature compensates substantially that of the mobility of the majority carriers in the channel of the MOS transistor of the cell so as to make its transconductance substantially independent of temperature.
- the polarization means may include a current mirror connected to the cell MOS transistor, this current mirror cooperating with a tuning circuit itself connected to a reference voltage generator, the tuning circuit comprising a MOS transistor okay crossed by the bias current that the current mirror copies and the voltage saturation grid of the tuning MOS transistor having a temperature slope substantially equal to and opposite to that of the mobility of majority carriers in the cell MOS transistor, this saturation gate voltage being obtained from the reference voltage generator.
- the tuning circuit may also include a bipolar transistor, the emitter of which is connected to one of the supply terminals through a resistor, the base of which is connected to the reference voltage generator and whose collector is connected on the one hand to the other terminal power supply through a series connection with a diode and a resistor and secondly to the gate of the tuning MOS transistor which is mounted between the other power supply terminal and the current.
- the reference voltage generator is intended to deliver to the tuning circuit a reference voltage to obtain a temperature slope such as that of the saturation gate voltage of the tuning MOS transistor substantially compensates for that of the mobility of the majority carriers in the cell's MOS transistor.
- Any conventional reference voltage generator for example a conventional reference voltage generator based on the energy band prohibited by a semiconductor material, can be used to obtain a reference voltage generator having the above characteristics.
- the voltage supplied by such a conventional generator has a given temperature dependence, generally between 0 and 1.
- the temperature dependence of the saturation gate voltage of the MOS transistor can be modified according to the invention to substantially compensate for that of mobility majority carriers in the cell's MOS transistor.
- the conventional generator is connected to a divider bridge including by example two resistors, one of the two being connected to the output of the conventional generator and the other to a ground, the midpoint between these two resistors being connected to the input of the circuit tuning, i.e. at the base of the tuning transistor.
- a divider bridge including by example two resistors, one of the two being connected to the output of the conventional generator and the other to a ground, the midpoint between these two resistors being connected to the input of the circuit tuning, i.e. at the base of the tuning transistor.
- the transconductance cell may include a differential pair of transistors MOS whose grids form the inputs of the transconductance circuit and drains the outputs.
- the differential pair of MOS transistors can cooperate with a degeneration resistor mounted between the sources of the MOS transistors of the pair.
- Degeneration resistance can be achieved by a pair of transistors MOS, each of them having its gate connected to the gate of one of the respective MOS transistors of the differential pair.
- the transconductance cell can be mounted between the two terminals supply via the polarization means on one side and a load circuit on the other.
- the charging circuit can be passive.
- the charging circuit can be formed based on current source cooperating with common mode servo system of the outputs of the transconductance circuit.
- Another object of the invention is to produce an integrator circuit from the circuit previous one and make its time constant substantially independent of temperature and of the manufacturing process.
- Such an integrator circuit does not need a servo circuit of the time constant.
- Such an integrator circuit includes at least one circuit transconductance thus defined, the output of which is connected to an integration capacitor made from MOS transistor.
- the present invention also relates to a filter which comprises at least one such integrator circuit.
- the present invention also relates to a delay circuit or an oscillator which include at least one such integrator circuit.
- the invention can thus be implemented in an apparatus for receiving and transmitting radio communications signals including a transconductance circuit according to the invention.
- a device can for example be a telephone.
- FIG. 1 very schematically shows a transconductance circuit in MOS technology according to the invention.
- This circuit transconductance comprises between a first supply terminal 20 brought to a potential high Vcc and a second supply terminal 21 brought to a low potential Vee, generally ground, at least one transconductance cell 100 with at least one MOS transistor.
- the transconductance cell 100 is represented in the form of a pair differential of MOS transistors M1, M1 'and it is connected to one of the supply terminals 21 by means of polarization 200 and to the other supply terminal 20 by through a charging circuit 300.
- the charging circuit 300 can be passive or active as we will see later.
- Other configurations of the transconductance cell are possible such as that illustrated in FIG. 4, the differential pair of transistors MOS is a very simple configuration.
- the polarization means 200 deliver to the MOS transistors of the transconductance cell 100 a bias current whose variation with temperature appreciably compensates for that of carrier mobility majority in the channel of the MOS transistors of cell 100 so that the transconductance Gm of the circuit is substantially constant and independent of temperature.
- the geometrical dimensions of the channel of the MOS transistors are perfectly controlled during manufacture.
- the value of the capacitance C ox of the oxide thickness on the other hand depends on the manufacturing process and may vary for transconductance circuits belonging to different batches.
- the polarization means 200 can be realized by a current mirror 2.1 which cooperates with a tuning circuit 2.2, itself connected to a reference voltage generator 2.3, the tuning circuit 2.2 comprising a MOS M7 transistor of agreement crossed by the bias current as the current mirror recopy and whose saturation grid voltage has a significantly temperature slope equal and opposite to that of the mobility of majority carriers in the transistor channel MOS of the transconductance cell 100, this saturation grid voltage being obtained at from the reference voltage generator.
- FIG. 3b shows in detail the current mirror 2.1 and the tuning circuit 2.2.
- FIG. 3b shows in detail the current mirror 2.1 and the tuning circuit 2.2.
- FIG. 3b shows in details in French patent application No. 01 16573 filed on December 20, 2001 at name of the Applicant.
- the charging circuit 300 is passive and is formed of a resistor R31, R32 connected respectively between one of the supply terminals 20 and the drains of the transistors M1, M1 'of the differential pair 100.
- the transistors M1, M1 'of the differential pair 100 are N-channel MOS transistors but they could be P-channel with appropriate inversions.
- the sources of the transistors M1, M1 'of the differential pair 100 are connected to the polarization means 200.
- the gates of the transistors M1, M1 'of the differential pair form the input e1, e1 'of the transconductance circuit while the output s1, s1' is done on the drains transistors M1, M'1 of the differential pair 100 which are themselves connected to the load circuit 300.
- the current mirror 2.1 comprises a controlled MOS transistor M61, M62 connected to each of the MOS transistors M1, M1 'of the differential pair of transistors 100 and a transistor MOS master M6 connected to the MOS transistor M7 tuning of the tuning circuit 2.2.
- the tuning circuit 2.2 has a bipolar transistor Q13, the emitter of which is connected to one of the supply terminals 21 through a resistor R13, the base of which is connected to the reference voltage generator 2.3 and the collector is connected to the gate of the MOS transistor M7 ok on the one hand and on the other hand to the other supply terminal 20 through a series connection formed by a resistor R14 and a diode, represented by a MOS transistor M8 mounted as a diode, i.e. the gate of which is connected to the drain. More precisely, the source of the MOS transistor M8 is connected to the other terminal supply 20, its drain being connected to the resistor R14 and to its grid.
- the reference voltage generator 2.3 imposes on the base of the transistor bipolar Q13 a voltage Vref whose variation with temperature is chosen so that the saturation grid voltage Vgt of the MOS transistor M7 of tuning connected to the current mirror 2.1 a the appropriate temperature slope to counteract that of carrier mobility majority in the channel of the MOS transistors M1, M1 ′ of the transconductance cell 100. From by their manufacture the point of operation of all the transistors is in the region of strong inversion, that is to say that the grid saturation voltage is equal to Vgt ⁇ VDS.
- Vgt (M7) Vgs (M7) - V T with Vgs (M7) source gate voltage of the tuning MOS transistor M7 and V T threshold voltage of the tuning MOS transistor M7.
- Vgt (M7) Vgs (R14) + Vgs (M8) with V (R14) voltage across the resistor R14 and Vgs (M8) source gate voltage of the M8 MOS transistor diode.
- Vgs (M8) ⁇ V T because the gate voltage at saturation of the MOS transistor M8 is very small.
- Vgt (M7) the saturated gate voltage of the MOS transistor M7 in accordance with the voltage V (R14) across the resistor R14: Vgt (M7) ⁇ V (R14).
- V PTAT V PTAT0 (1 + t)
- V BE V BE0 (1 - t / 2) with V PTAT0 and V BE0 voltages at the reference temperature.
- V BE0 0.8V .
- ⁇ 2 can be considered negligible except for the gain in current ⁇ of the bipolar transistors.
- the reference voltage generator Vref 2.3 of Figure 3A consists of a conventional reference generator CVG and supplying a voltage VB having a temperature dependence which can be arbitrary. Often this dependence is zero but it can be modified according to the invention.
- the generator classic CVG delivers a reference voltage based on the forbidden energy band of a semiconductor material.
- a divider bridge including for example two resistors R110 and R111 is connected to the output of the CVG reference generator.
- One of the two R110 resistors has one of its terminals connected to the output of the conventional generator CVG which delivers the voltage VB and the other resistor has one of these terminals connected to a low potential Vee, generally the ground.
- the two resistors R110 and R111 have a common point at which the output of the reference voltage generator 2.3.
- FIG 3B provides a detailed example of a reference voltage generator improved allowing the delivery of a voltage whose temperature dependence is controlled.
- the reference voltage generator Vref 2.3 of Figure 3B consists of a input stage 1 with two branches 10, 11 mounted between the two supply terminals 20, 21. In each of the branches 10, 11 there is at least bipolar transistor Q1, Q2 and these transistors do not have the same size of transmitter.
- This input circuit 1 combines a base voltage emitter of one of the bipolar Q2 transistors with a voltage proportional to the temperature absolute. More precisely, the two transistors Q1, Q2 have their common base, their collectors connected to the supply terminal 20 brought to the potential Vcc via a resistor R2, R3 respectively.
- the emitter of the first transistor Q1 is connected to the other terminal supply 21 via a series 12 mounting of two resistors R1, R0.
- the transmitter of the second transistor Q2 is connected to the other supply terminal 21 via one R0 of the resistors of the assembly series 12.
- the emitter area of the first transistor Q1 is equal to n (n integer greater than a) times that of the second transistor Q2.
- n can be equal to 8.
- This input stage 1 cooperates with an operational amplifier 2 which includes a differential amplifier stage 13, an output stage 14, a compensation circuit 16.
- the output stage 14 delivers the reference voltage Vref, it is connected by a loop 3 at the input stage 1 at the level of the common base of the two transistors Q1, Q2 of the stage input 1.
- the differential amplifier stage 13 comprises a pair of transistors Q6, Q7 differential 15 connected to the input stage 1 and mounted between the two supply terminals 20, 21 via a source circuit 17 and a load circuit 18. More precisely, the bases of the two transistors Q6, Q7 form the two differential inputs of stage 13.
- the base of transistor Q6 is connected to branch 11 at the collector of transistor Q2, the base of transistor Q7 is connected to branch 10 at the collector of transistor Q1.
- the emitters of transistors Q6, Q7 are interconnected. They are connected to the power terminal 21 brought to the potential Vee by the source circuit 17 which is an active circuit.
- the circuits of source 17 and load 18 include regulation means R8, R9 for, even when the loop 3 is open, regulate the reference voltage Vref, the latter being adjusted by substantially independent of the manufacturing process, variations in voltage Vcc-Vee power supply and with a predetermined temperature slope.
- the source circuit 17 comprises in series a diode, represented by a transistor Q9 connected by diode, and a resistor R9 forming part of the regulation means.
- the resistor R9 is connected to the common emitters of the transistors Q6, Q7 of the differential pair 15.
- the collectors of the two transistors Q6, Q7 are each connected to the supply terminal 20 brought to potential Vcc via the charging circuit 18.
- This charging circuit 18 includes a resistor R8, part of the regulation means, mounted between the collector of the transistor Q7 of the differential pair and the supply terminal 20.
- the collector of the other transistor Q6 of the differential pair 15 is directly connected to the terminal supply 20.
- the output stage 14 is connected in a first node A to the charging circuit 18, at the collector of transistor Q7.
- the ratio of resistances R9 and R8 of the regulation means is chosen in such a way that a variation ⁇ (Vcc-Vee) of the supply voltage results appreciably the same variation ⁇ (Vcc-Vee) on the source circuit 17 and on the load circuit 18 aux load resistor R8 terminals whatever the temperature. Consequently, the first node A does not vary in voltage during a variation of the supply voltage.
- the ratio of resistances R8 / R9 of the regulation means is chosen in such a way that the gain in common mode of resistors R2, R3 is adjusted to the value -1. This is achieved when the ratio of the resistance values R8 / R9 is approximately 2, the current in the resistance R9 being substantially equal to twice that crossing the load resistance R8.
- the source circuit 17 is configured to generate a current substantially independent of temperature, which means that the resistance R9 is adjusted so that the voltage across its terminals is substantially independent of the temperature. This is checked for all temperatures if the next adjustment is made at input stage 1.
- V R9 (Vcc - Vee) - (V R3 + V BE (Q6) + V BE (Q9))
- V R9 (Vcc - Vee) - (V R3 + 2V BE )
- V R3 + 2V BE The term (V R3 + 2V BE ) must then be substantially independent of the temperature, this happens if it is equal to twice the voltage present at the connection between the loop 3 and the output stage 14, for example and if the temperature slope of the peak resistance R3 compensates for those of the two base-emitter voltages of the transistors Q6 and Q9. This makes the reference voltage generator substantially insensitive to the manufacturing process. With the notation explained previously, the temperature slope of the resistor R3 is substantially equal to one and that of the voltage across the resistor R9 substantially equal to zero.
- the two resistors R2, R3 of the collector of the input stage 1 are identical.
- the output stage 14 comprises a follower circuit 22 with a transistor Q5 of which the transmitter is connected to the power supply terminal 21 through a resistor bridge R110, R111.
- the base of transistor Q5 is connected to the first node A while the emitter of transistor Q5 is connected to loop 3 when it is closed at a second node B.
- Resistor R110 is connected to the emitter of transistor Q5, the resistor R111 is connected to the supply terminal 21.
- the two resistors R110 and R111 have a common point C at which the output of the reference voltage generator 2.3. We find here in a more elaborate form the use of a divider bridge.
- the output stage 14 further comprises an adjustment circuit 24 which generates a current whose temperature slope is substantially equal to +1.5 and this slope is adjusted by the values of resistors R110, R111 of the divider bridge and more particularly by the ratio (R110 + R111) / R111. By giving this ratio substantially the value 8/9, the current crossing resistance R12 has a substantially +1.5 slope.
- This adjustment circuit 24 comprises a transistor Q12, the emitter of which is connected to the supply terminal 21 through a resistor R12, the collector of which is connected to the first node A and to the collector of the compensation 16 and whose base is connected to the follower circuit 22.
- the base of transistor Q12 is connected to the common point C and it is at the base of the transistor Q12 that the output of the reference voltage generator.
- the current flowing in the adjustment circuit 24 will be copied throughout Q13, R13 of the tuning circuit 2.2 described in FIG. 2. Indeed this set Q13, R13 forms a current mirror with adjustment circuit 24.
- the resistors R13 and R12 are the same.
- the temperature slope at the point common C which corresponds to the output of the reference voltage generator 2.3 must be substantially equal to zero. To achieve this, we will now see the action of the circuit of compensation 16 and of the adjustment circuit 24 on the temperature slope at the first node A.
- the temperature slope of the voltage at the first node A must be appreciably equal to and opposite to that provided by transistor Q5 of output stage 14 to obtain the slope compensation at common point C. It follows that the temperature slope of the voltage at the first node A must be substantially equal to 0.5 since the temperature slope of a base emitter voltage of a bipolar transistor is -0.5. This slope is conditioned by that of the source circuit 17 and that of the compensation circuit 16 associated with the adjustment 24.
- These three circuits each include a bipolar transistor Q9, Q10, Q12, the temperature slope is imposed and equal to substantially -0.5 and a resistance R9, R10, R12 that it suffices to adjust to impose that of the charging circuit 18.
- the temperature slope of the compensation circuit 16 cooperating with adjustment circuit 24 thus takes substantially value slightly greater than one in the example described and that of the source circuit 17 substantially the value 0.
- the currents generated by the compensation circuit 16 and by the adjustment circuit 24 combine at the charge circuit 18 and the current resulting in the charge circuit load has a temperature slope which depends on the relative weights of the currents of the two circuits, i.e. values of resistors R10, R12. In the example described, it is preferable that the slope due to compensation circuits 16 and adjustment 24 be slightly greater than one to get rid of inevitable second-order parasites which have an action of reduction in the value of the slope.
- a circuit for stabilization 19 of the differential amplifier 13 It is preferable to provide, in the operational amplifier 2, a circuit for stabilization 19 of the differential amplifier 13. It can be achieved by a capacitor C1 connected between node A and supply terminal 21.
- All bipolar transistors have been represented by NPN transistors, but there it is possible to replace them with PNP bipolar transistors by performing all appropriate reversals, in particular at the level of the load and source circuits.
- FIG. 4 shows an example of an integrator circuit made from a circuit with transconductance according to the invention.
- This integrating circuit includes a circuit substantially constant transconductance 40 and an integration capacitor 41 connected in output of the transconductance circuit.
- the time constant T of this integrating circuit is independent of the temperature and circuit manufacturing process.
- the gate of the MOS transistor carrying out the capacitor C is connected to output s1, the drain, the channel and the source of the MOS transistor to the output s1 '.
- the transconductance circuit 40 always includes the cell to transconductance 100 mounted between a bias circuit 200 and a charge circuit 300.
- the transconductance circuit 40 is not of the same type as that of FIG. 2.
- the transconductance cell 100 always has a differential pair 101 MOS transistors M1, M1 '.
- This differential pair 101 of transistors is now cooperating with a degenerative resistance 102 represented in this example in the form of a pair of degeneracy MOS transistors M2, M2 ', each of the pair's MOS transistors differential M1, M1 'is associated with one of the degeneration MOS transistors M2, M2' respectively.
- a degeneration resistor 102 produced with MOS transistors brings a better linearity than a degeneration resistance in polycrystalline silicon.
- the optimal linearity is obtained when the ratio W1 / L1 of the width over the length of the channel of the differential pair MOS transistors 101 is substantially equal to seven times the ratio W2 / L2 of the width over the length of the channel of the MOS transistors of the resistance degeneration 102.
- the two MOS transistors M1, M1 'of the differential pair 101 have their gates which form the inputs e1, e1 'of the integrating circuit. Their sources are linked to the supply terminal 20 brought to the potential Vcc through the load circuit 300 and their drains at supply terminal 21 brought to potential Vee through the bias circuit 200. It is assumed that the bias circuit 200 is similar to that shown in the figures 2 and 3.
- the output s1, s1 'of the transconductance circuit 40 is made at the drains of the MOS transistors M1, M1 'of the differential pair 101.
- the integration capacitor C is mounted between the two outputs s1, S1 'of the transconductance circuit.
- MOS transistors M1, M1 'of the differential pair 101 are connected to the transistors MOS M2, M2 'of degeneration 102 as follows: each of the sources of MOS transistors M1, M1 ′ is connected on the one hand to the source of one of the MOS transistors of degeneration M2, M2 'respectively and to the drain of the other MOS transistor of degeneration M2 ', M2 respectively.
- the grid of each of the MOS M2, M2 'transistors of degeneration is connected to the gate of the MOS transistor M1, M1 'of the differential pair 101 with which he is associated.
- the charging circuit 300 is now represented as an active circuit under the form of two current sources 301 equipped with a mode control system common 302 of outputs s1, s1 'of the transconductance circuit 40 so as to stabilize the common mode output voltage.
- the charging circuit can also be a simple charging circuit as known to those skilled in the art and simply including resistors.
- the common mode servo system is an improved embodiment.
- MOS transistors M2, M2 'of degeneration 102 operate in linear mode. They are of the same type as the MOS transistors M1, M1 'of the differential pair and therefore have the same mobility of the majority carriers ⁇ and the same saturation grid voltage Vgt as the MOS transistors M1, M1' of the differential pair 101.
- I2 ( ⁇ C ox W2 / L2) Vgt.Vds with ⁇ mobility of the majority carriers in the channel of the MOS transistors M2, M2 ', C ox capacity per unit area of the oxide layer of the MOS transistors, W2 / L2 ratio of the width W2 over the length L2 of the channel of the MOS transistors, Vgt saturation gate voltage of the MOS transistors and Vds drain-source voltage of the MOS transistors.
- T Gm / C with C capacitance of capacitor C.
- T 1 2.75 ⁇ C ox ⁇ W1 L1 Vgt VS ox W vs ⁇ L vs
- the product W c L c corresponds to the product of the width W c by the length L c of the channel of the MOS transistors producing the capacitor C.
- T 1 2.75 ⁇ W1 L1.W vs .L vs . ⁇ .Vgt
- the constant of time T no longer depends on the manufacturing process because the capacity C ox is eliminated in its expression.
- T F. ⁇ .Vgt
- the time constant now only depends on a geometric factor F which is a function of W1 / L1 and of W c L c of the MOS transistors, of the mobility of the majority carriers ⁇ and of Vgt.
- Such an integrator circuit can operate with amplitudes of input signals more important than those of an integrator circuit of the prior art with a cell to transconductance having only a differential pair of MOS transistors.
- FIG. 5 shows the variations of different quantities depending on the temperature in an integrating circuit such as that of FIG. 4.
- the curve referenced 1 represents the variations of the transconductance Gm of the transconductance circuit 40
- the curve referenced 2 represents the current I1
- the curve 3 represents the saturation grid voltage Vgt of the MOS transistors of the transconductance cell.
- the bias current of the MOS transistors of the transconductance cell dependent on the adaptation of critical resistances or transistors of the voltage generator and the current mirror, the size of these components must be carefully adjusted to obtain the desired precision.
- the time constant obtained with the integrating circuit in Figure 4 has an accuracy of about 3% due to variations in the temperature of the supply voltage, approximately 1.3% due to the aperage between components and approximately 1.6% due to the manufacturing process.
- Such an integrating circuit can be used as a filter. It can serve as a block of base in an oscillator circuit as illustrated in figure 6A or in a delay circuit as shown in Figure 6B.
- FIG. 6A there are two conforming integrator circuits to the invention connected in series CI1, CI2, the output of the second integrator circuit CI2 being connected to an amplifier A1 of gain -1.
- the output of amplifier A1 is looped over the input of first integrator circuit CI1.
- Each of the integrating circuits is schematized by a transconductance amplifier GM1, GM2 polarized by a current source I10, I20.
- the output of amplifiers GM1, GM2 is connected to an electrode of an integration capacitor C10, C20 with the other electrode grounded. Better frequency accuracy oscillation is obtained using the integrator circuits of the invention.
- the delay circuit comprises an integrator circuit CI according to the invention, the output of which is connected to a delay cell D.
- the output of the delay circuit is done at the output of delay cell D while the input is at the input of the integrator circuit CI.
- the integrator circuit CI is shown diagrammatically as in the figure 6A with a transconductance amplifier GM1 polarization means I10 and a integration capacitor C10.
- circuits described in these latter figures can advantageously be used in an apparatus intended for the reception and / or transmission of radio telecommunications signals including a transconductance circuit with improved performance according to the invention.
- the insertion of such transconductance circuits in such devices is known from the skilled person.
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Abstract
Description
Gm= dId/dVgs à saturation soit
Gm= (µCoxW/L)(Vgs - VT), la différence Vgs-VT correspondant à Vgt ou tension grille de saturation des transistors MOS M1, M1'.
Vgs(M7) = V(R14) + Vgs(M8) avec V(R14) tension aux bornes de la résistance R14 et Vgs(M8) tension grille source du transistor MOS M8 monté en diode.
Vgt(M7) ≈ V(R14).
T = (T - T0)/T0, avec T température considérée et T0 température de référence par exemple égale à 25°C. Les valeurs de t suivantes sont obtenues par rapport aux températures T courantes :
V = V0(a + bt + ct2) avec V0 valeur de la tension à la température de référence T0 et a, b, c des coefficients. La pente en température au premier ordre est donnée par :
α1 = b/a et la pente en température au second ordre est donnée par α2 = c/a.
VPTAT = VPTAT0(1 + t) et pour une tension base-émetteur d'un transistor bipolaire :
VBE = VBE0(1 - t/2) avec VPTAT0 et VBE0 tensions à la température de référence. Pour un transistor bipolaire VBE0 = 0,8V.
NOM | VALEUR | PENTE | CHUTE DE TENSION |
Vcc-Vee | 2,8 | 0 | - |
R2, R3 | 16,8 kΩ | 1 | 0,8 V |
Vbe(Q1, Q2, Q6, Q7, Q5, Q9, Q10, Q12, Q13) | -0,5 | 0,8 V | |
R1 | 1 kΩ | 1 | 0,05 V |
R0 | 4,2 kΩ | 1 | 0,4 V |
R8 | 10 kΩ | 0,5 | 0,8 V |
R9 | 4,1 kΩ | 0 | 0,4V |
R10 | 40 kΩ | 1 | 0,4 V |
R12, R13 | 15 kΩ | 1,5 | 0,27 V |
R110 | 1 kΩ | - | - |
R111 | 8kΩ | - | - |
I1 = ½(µCoxW1/L1)Vgt2 avec µ mobilité des porteurs majoritaires dans le canal des transistors MOS M1, M1', Cox capacité par unité de surface de la couche d'oxyde des transistors MOS, W1/L1 rapport de la largeur W1 sur la longueur L1 du canal des transistors MOS, Vgt tension grille de saturation des transistors MOS. La transconductance gm1 de la paire différentielle est donnée par :
gm1 = β1Vgt avec β1 = µCoxW1/L1
I2 = (µCoxW2/L2)Vgt.Vds avec µ mobilité des porteurs majoritaires dans le canal des transistors MOS M2, M2', Cox capacité par unité de surface de la couche d'oxyde des transistors MOS, W2/L2 rapport de la largeur W2 sur la longueur L2 du canal des transistors MOS, Vgt tension grille de saturation des transistors MOS et Vds tension drain-source des transistors MOS.
T = Gm/C avec C capacité du condensateur C.
Claims (13)
- Circuit à transconductance avec au moins une cellule à transconductance (100) montée entre deux bornes d'alimentation (20, 21) incluant au moins un transistor MOS (M1, M1'), caractérisé en ce qu'il comporte des moyens (200) pour polariser le transistor MOS (M1, M1') de la cellule (100) avec un courant de polarisation dont la variation en fonction de la température compense sensiblement celle de la mobilité des porteurs majoritaires dans le canal du transistor MOS (M1, M1') de la cellule (100) de manière à rendre sa transconductance sensiblement indépendante de la température.
- Circuit à transconductance selon la revendication 1, caractérisé en ce que les moyens de polarisation (200) comportent un miroir de courant(2.1) relié au transistor MOS (M1, M1') de la cellule (100), ce miroir de courant (2.1) coopérant avec un circuit d'accord (2.2) lui-même relié à un générateur de tension de référence (2.3), le circuit d'accord (2.2) comportant un transistor MOS (M7) d'accord traversé par le courant de polarisation que le miroir de courant (2.1) recopie, la tension grille de saturation (Vgt) du transistor MOS (M7) d'accord possédant une pente en température sensiblement égale et opposée à celle de la mobilité des porteurs majoritaires dans le canal du transistor MOS (M1, M1') de la cellule (100), cette tension grille de saturation étant obtenue à partir du générateur de tension de référence (2.3).
- Circuit à transconductance selon la revendication 2, caractérisé en ce que le circuit d'accord (2.2) comporte de plus un transistor bipolaire (Q13) dont l'émetteur est relié à l'une des bornes d'alimentation (21) à travers une résistance (R13), dont la base est reliée au générateur de tension de référence (2.3) et dont le collecteur est relié d'une part à l'autre borne d'alimentation (20) à travers un montage série avec une diode ((M8) et une résistance (R14) et d'autre part à la grille du transistor MOS (M7) d'accord qui est monté entre l'autre borne d'alimentation (20) et le miroir de courant (2.1).
- Circuit à transconductance selon l'une des revendications 2 ou 3, caractérisé en ce que le générateur de tension de référence (2.3) délivre au circuit d'accord (2.2) une tension de référence (Vref) dont la pente en température et la valeur sont choisies pour que la pente en température de la tension grille de saturation du transistor MOS (M7) d'accord compense sensiblement celle de la mobilité des porteurs majoritaires dans le transistor MOS (M1, M1') de la cellule (100).
- Circuit à transconductance selon l'une des revendications 1 à 4, caractérisé en ce que la cellule à transconductance (100) comporte une paire différentielle de transistors MOS (M1, M1') dont les grilles forment les entrées (e1, e1') du circuit à transconductance et les drains les sorties (s1, s1').
- Circuit à transconductance selon la revendication 5, caractérisé en ce que la paire différentielle de transistors MOS (M1, M1') coopère avec une résistance de dégénérescence (M2, M2') montée entre les sources des transistors MOS (M1, M1') de la paire.
- Circuit à transconductance selon la revendication 6, caractérisé en ce que la résistance de dégénérescence est réalisée par une paire de transistors MOS (M2, M2'), chacun d'entre eux ayant sa grille reliée à la grille de l'un des transistors MOS (M1, M1') respectif de la paire différentielle.
- Circuit à transconductance selon l'une des revendications 1 à 7, caractérisé en ce que la cellule à transconductance (100) est montée entre les deux bornes d'alimentation (20, 21) à travers d'un côté les moyens de polarisation (200) et de l'autre un circuit de charge (300).
- Circuit intégrateur caractérisé en ce qu'il comporte un circuit à transconductance selon l'une des revendications 1 à 8 dont la sortie est connectée à un condensateur d'intégration (C ) réalisé à partir de transistor MOS.
- Filtre caractérisé en ce qu'il comporte au moins un circuit intégrateur selon la revendication 9.
- Oscillateur caractérisé en ce qu'il comporte au moins un circuit intégrateur selon la revendication 9.
- Circuit retardateur caractérisé en ce qu'il comporte au moins un circuit intégrateur selon la revendication 9.
- Appareil destiné à la réception et/ou à la transmission de signaux de radiotélécommunication incluant un circuit de transconductance selon l'une des revendications 1 à 8.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0116577A FR2834087A1 (fr) | 2001-12-20 | 2001-12-20 | Circuit a transconductance sensiblement constante |
FR0116577 | 2001-12-20 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1324170A1 true EP1324170A1 (fr) | 2003-07-02 |
Family
ID=8870774
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP02080252A Withdrawn EP1324170A1 (fr) | 2001-12-20 | 2002-12-11 | Circuit à transconductance sensiblement constante |
Country Status (4)
Country | Link |
---|---|
US (1) | US6693467B2 (fr) |
EP (1) | EP1324170A1 (fr) |
CN (1) | CN100337329C (fr) |
FR (1) | FR2834087A1 (fr) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10147101A1 (de) * | 2001-09-25 | 2003-04-24 | Infineon Technologies Ag | Temperaturstabilisierte Verstärkerschaltung |
US7071673B2 (en) * | 2003-09-02 | 2006-07-04 | Acu Technology Semiconductor Inc. | Process insensitive voltage reference |
ATE441244T1 (de) * | 2003-10-13 | 2009-09-15 | Nxp Bv | Transkonduktanz-schaltung |
EP1589657A1 (fr) * | 2004-04-19 | 2005-10-26 | CSEM Centre Suisse d'Electronique et de Microtechnique SA | Circuit d'asservissement de la transconductance d'au moins un transistor en conduction |
US7532045B1 (en) * | 2005-02-08 | 2009-05-12 | Sitel Semiconductor B.V. | Low-complexity active transconductance circuit |
CN100386706C (zh) * | 2005-02-25 | 2008-05-07 | 清华大学 | 调整负载中晶体管跨导变化范围用的偏置补偿电路 |
US7307476B2 (en) * | 2006-02-17 | 2007-12-11 | Semiconductor Components Industries, L.L.C. | Method for nullifying temperature dependence and circuit therefor |
US7710165B2 (en) * | 2007-09-25 | 2010-05-04 | Integrated Device Technology, Inc. | Voltage-to-current converter |
TWI365601B (en) * | 2007-09-27 | 2012-06-01 | Mstar Semiconductor Inc | High linearity mixer with programmable gain and associated transconductor |
JP2013219569A (ja) * | 2012-04-10 | 2013-10-24 | Seiko Epson Corp | トランスコンダクタンス調整回路、回路装置及び電子機器 |
US9450540B2 (en) * | 2015-01-12 | 2016-09-20 | Qualcomm Incorporated | Methods and apparatus for calibrating for transconductance or gain over process or condition variations in differential circuits |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4823092A (en) * | 1985-05-28 | 1989-04-18 | Wolfson Microelectronics Limited | MOS transconductance amplifier for active filters |
EP0543056A1 (fr) * | 1990-09-20 | 1993-05-26 | Delco Electronics Corporation | Générateur de courant dépendant de la température |
EP0740243A2 (fr) * | 1995-04-24 | 1996-10-30 | Samsung Electronics Co., Ltd. | Convertisseur tension/courant |
US5748030A (en) * | 1996-08-19 | 1998-05-05 | Motorola, Inc. | Bias generator providing process and temperature invariant MOSFET transconductance |
EP0911978A1 (fr) * | 1997-10-23 | 1999-04-28 | STMicroelectronics S.r.l. | Génération de tension de référence symétriques à faible bruit et compensées en température |
US5978240A (en) * | 1997-10-07 | 1999-11-02 | Stmicroelectronics S.R.L. | Fully differential voltage-current converter |
US5986910A (en) * | 1997-11-21 | 1999-11-16 | Matsushita Electric Industrial Co., Ltd. | Voltage-current converter |
US6265929B1 (en) * | 1998-07-10 | 2001-07-24 | Linear Technology Corporation | Circuits and methods for providing rail-to-rail output with highly linear transconductance performance |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6259307B1 (en) * | 1998-10-14 | 2001-07-10 | Texas Instruments Incorporated | Temperature compensated voltage gain stage |
JP3841195B2 (ja) * | 1998-12-02 | 2006-11-01 | 富士通株式会社 | 差動増幅器 |
US6323732B1 (en) * | 2000-07-18 | 2001-11-27 | Ericsson Inc. | Differential amplifiers having β compensation biasing circuits therein |
US6448848B1 (en) * | 2000-12-29 | 2002-09-10 | Intel Corporation | Method of controlling common-mode in differential gm-C circuits |
-
2001
- 2001-12-20 FR FR0116577A patent/FR2834087A1/fr active Pending
-
2002
- 2002-12-11 EP EP02080252A patent/EP1324170A1/fr not_active Withdrawn
- 2002-12-17 US US10/321,200 patent/US6693467B2/en not_active Expired - Lifetime
- 2002-12-17 CN CNB021563896A patent/CN100337329C/zh not_active Expired - Fee Related
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4823092A (en) * | 1985-05-28 | 1989-04-18 | Wolfson Microelectronics Limited | MOS transconductance amplifier for active filters |
EP0543056A1 (fr) * | 1990-09-20 | 1993-05-26 | Delco Electronics Corporation | Générateur de courant dépendant de la température |
EP0740243A2 (fr) * | 1995-04-24 | 1996-10-30 | Samsung Electronics Co., Ltd. | Convertisseur tension/courant |
US5748030A (en) * | 1996-08-19 | 1998-05-05 | Motorola, Inc. | Bias generator providing process and temperature invariant MOSFET transconductance |
US5978240A (en) * | 1997-10-07 | 1999-11-02 | Stmicroelectronics S.R.L. | Fully differential voltage-current converter |
EP0911978A1 (fr) * | 1997-10-23 | 1999-04-28 | STMicroelectronics S.r.l. | Génération de tension de référence symétriques à faible bruit et compensées en température |
US5986910A (en) * | 1997-11-21 | 1999-11-16 | Matsushita Electric Industrial Co., Ltd. | Voltage-current converter |
US6265929B1 (en) * | 1998-07-10 | 2001-07-24 | Linear Technology Corporation | Circuits and methods for providing rail-to-rail output with highly linear transconductance performance |
Also Published As
Publication number | Publication date |
---|---|
CN1427480A (zh) | 2003-07-02 |
CN100337329C (zh) | 2007-09-12 |
US6693467B2 (en) | 2004-02-17 |
FR2834087A1 (fr) | 2003-06-27 |
US20030132787A1 (en) | 2003-07-17 |
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