CN114900134A - Neutralizing capacitor amplifier and terminal of strip electrode isolation MOS (metal oxide semiconductor) tube - Google Patents

Abstract

The invention belongs to the technical field of wireless communication, and discloses a belt body electrode isolation MOS tube neutralization capacitor amplifier and a terminal, wherein the belt body electrode isolation MOS tube neutralization capacitor amplifier is provided with a first MOS tube, a second MOS tube, a third MOS tube and a fourth MOS tube; the grid electrode in the first MOS tube is connected with a positive phase input signal end Vin +, and the drain electrode in the first MOS tube is connected with a positive phase output signal end Vout +; the grid electrode in the second MOS tube is connected with an inverting input signal end Vin-, and the drain electrode in the second MOS tube is connected with a negative phase output signal end Vout-; a source electrode in the third MOS tube is connected with the first resistor, and a body electrode in the third MOS tube is connected with the second resistor; and the source electrode in the fourth MOS tube is connected with the first resistor. The invention can improve the gain of the amplifier, optimize the noise coefficient of the amplifier and contribute to the improvement of the overall performance of the radio frequency chip.

Description

A kind of body electrode isolation MOS tube neutralizing capacitor amplifier and terminal

technical field

The invention belongs to the technical field of wireless communication, and in particular relates to a neutralization capacitor amplifier and a terminal of a MOS tube with body electrode isolation.

Background technique

At present, in the design process of the RF amplifier, due to the feedback effect of the gate-drain capacitance C _gd of the MOS transistor, the amplified signal of the drain is introduced into the gate input terminal, which easily causes the amplifier to oscillate and affects the working state of the amplifier. Therefore, the neutralization capacitor technology is often used, and the gate of the MOS tube at one end of the differential amplifier is connected with the drain of the MOS tube at the other end with a capacitor. Since the drains of the MOS tubes at both ends are opposite in phase, it can cancel the C _gd . effect. After introducing the neutralizing capacitor C _n , the stability factor of the amplifier is:

Among them, ω is the angular frequency, R _g is the gate resistance, R _d is the load resistance, and g _m is the transconductance of the MOS tube. When k is greater than or equal to 1, the amplifier is unconditionally stable. Therefore, only when the size of the neutralization capacitor C _n is similar to that of C _gd , the denominator of k is close to zero, and k becomes very large, and the amplifier can be stable.

At present, the most commonly used neutralizing capacitors are MIM capacitors composed of metal plates and MOM capacitors composed of metal fingers. The capacitance of these two capacitors is related to the processing of the metal, and will not occur with the process deviation of the MOS tube. changes, so there is no guarantee that the effect of C _gd can be counteracted at different process angles. As shown in Figure 6, the metal capacitor is regarded as a capacitor with a constant capacitance value, and the capacitance value of the capacitor is designed according to the standard process angle tt, and the Gmax of the simulated amplifier varies with frequency under different process angles. The Gmax curve is usually divided into two sections, the low-frequency part is MSG, which is the maximum gain the amplifier can achieve in steady state, and the high-frequency part is MAG, which is the maximum gain the amplifier can achieve. The part of MAG indicates that the amplifier is unconditionally stable in this frequency band. In the figure, the solid line is the tt process angle, and the neutralization capacitor is designed according to this process angle, so there is almost no MSG curve, the dotted line is the ss process angle, and the dashed line is the ff process angle. It can be seen that the Gmax curve of the amplifier has a clear MSG interval at the ff and ss process angles, and the turning point from MSG to MAG is around 10GHz. If the performance of the MOS tube processed by the amplifier is in the ff or ss process angle, the amplifier may oscillate at a frequency within 10GHz.

The closest existing technology is a technology in which the C _gd of the MOS tube is used as a neutralizing capacitor, and the body electrode and the source electrode of the MOS tube used as a neutralizing capacitor are connected to a large resistor. The basic circuit is shown in Figure 2. shown. In the figure, M1 and M2 are the core MOS tubes of the amplifier, used to amplify the signal, M3 and M4 are the neutralizing capacitor MOS tubes, Load1 and Load2 are the loads of the amplifier, and R1 is the tail resistor. When the value of R1 is very large, there is almost no current passing through M3 and M4, and M3 and M4 work in an almost cut-off state. One end of C _gd of M3 and M1 is connected to the non-inverting input signal Vin+, and the other end is connected to Vout- and Vout+ respectively. The phases are opposite, so they can cancel each other. Similarly, the C _gd of M4 and M2 can also cancel each other. Due to the same type of MOS transistors placed together, the changes in ion implantation concentration and gate oxide thickness caused by process deviation are synchronized, so the offset effect of C _gd will basically not change due to process deviation. can be very stable. Although the above-mentioned neutralizing capacitor scheme makes the amplifier stability against process fluctuations, there are still many problems, and the corresponding disadvantages are as follows: Short to one end of the large resistor, the parasitic capacitance C _db between the drain electrodes and the body electrodes of M3 and M4 and some parasitic resistances will form a path between the drains of M1 and M2, which will lose the output power and reduce the amplifier gain. The noise of the amplifier is poor. The noise performance of the amplifier in the RF link is usually measured by the noise figure, which is usually inversely proportional to the transconductance _gm of the amplifier. Therefore, the gain of the amplifier is reduced, which is equivalent to reducing the amplifier's performance. g _m , which in turn increases the noise figure. At the same time, in the path formed by C _db of M3 and M4 and some parasitic resistances, the parasitic resistance will introduce resistance thermal noise into the output terminal, further deteriorating the output noise.

Through the above analysis, the existing problems and defects in the prior art are:

(1) Compared with the prior art, the gain of metal neutralization capacitance will be reduced. The source and body electrodes of M3 and M4 are short-circuited to one end of the large resistance, and the parasitic capacitance C _db between the drain electrode and the body electrode of M3 and M4 and some The parasitic resistance creates a path between the drains of M1 and M2 that loses output power and reduces the gain of the amplifier.

(2) The noise of the amplifier in the prior art is poor, and the noise performance of the amplifier in the radio frequency chain is usually measured by the noise figure, which is usually inversely proportional to the transconductance _gm of the amplifier, so the gain of the amplifier is reduced , which effectively reduces the amplifier's g _m , which in turn increases the noise figure. At the same time, in the path formed by C _db of M3 and M4 and some parasitic resistances, the parasitic resistance will introduce resistance thermal noise into the output terminal, further deteriorating the output noise.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the present invention provides a neutralization capacitor amplifier and a terminal of a MOS transistor with body electrode isolation.

The present invention is realized in this way, a neutralization capacitor amplifier with body electrode isolation MOS transistor, wherein the neutralization capacitor amplifier with body electrode isolation MOS transistor is provided with a first MOS transistor, a second MOS transistor, a third MOS transistor, a third MOS transistor, and a third MOS transistor. Four MOS tubes;

The gate in the first MOS tube is connected to the non-inverting input signal terminal Vin+, the drain in the first MOS tube is connected to the non-inverting output signal terminal Vout+; the gate in the second MOS tube is connected to the inverting input signal terminal Vin-, The drain in the two MOS tubes is connected to the negative phase output signal terminal Vout-;

The source electrode of the third MOS transistor is connected to the first resistor, the body electrode of the third MOS transistor is connected to the second resistor; the source electrode of the fourth MOS transistor is connected to the first resistor, and the body electrode of the fourth MOS transistor is connected to the third resistor. resistance.

Further, the first MOS transistor is provided with a source electrode and a body electrode, and the source electrode and the body electrode are grounded.

Further, the second MOS transistor is provided with a source electrode and a body electrode, and the source electrode and the body electrode are grounded.

Further, the third MOS transistor is provided with a gate, the gate is connected to the positive-phase input signal terminal Vin+, and the drain of the third MOS transistor is connected to the negative-phase output signal terminal Vout-.

Further, the fourth MOS transistor is provided with a gate, the gate is connected to the inverting input signal terminal Vin-, and the drain of the fourth MOS transistor is connected to the non-inverting output signal terminal Vout+.

Further, the non-inverting output signal terminal Vout+ is connected to the first load, and the first load is connected to the power supply Vdd.

Further, the negative phase output signal terminal Vout- is connected to the second load, and the second load is connected to the power supply Vdd.

Further, one end of the first resistor is grounded, one end of the second resistor is grounded, and one end of the third resistor is grounded.

Further, the first MOS transistor and the second MOS transistor have the same size, and the third MOS transistor and the fourth MOS transistor have the same size;

The size of the second resistor and the third resistor are the same, and the values of the first resistor, the second resistor and the third resistor are in the order of kiloohm and above.

Another object of the present invention is to provide a wireless communication terminal, wherein the wireless communication terminal is installed with the strip electrode isolation MOS transistor neutralization capacitor amplifier.

Another object of the present invention is to provide a radio frequency chip, the radio frequency chip includes the strip body electrode isolation MOS transistor neutralization capacitor amplifier.

In conjunction with the above-mentioned technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are analyzed from the following aspects:

First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, closely combine the technical solutions to be protected of the present invention and the results and data in the research and development process, etc., and analyze in detail and profoundly how to solve the technical solutions of the present invention. Technical problems, some creative technical effects brought about by solving problems. The specific description is as follows:

In the present invention, the body electrodes of the two MOS tubes are respectively connected to the large resistance to the ground, the source electrodes are interconnected and then connected to the ground, and the two MOS tubes working in the cut-off region are cross-connected to the two core MOS tubes of the amplifier. Between the gate and the drain, the C _gd of the two cancel each other out, so as to realize the full-band stability of the amplifier. The DC potentials of the drain and body electrodes of the MOS transistor used as the neutralizing capacitor and the core MOS transistor of the amplifier are the same, and C _gd is similarly affected by process deviations. Therefore, the neutralizing capacitor of the present invention can follow the process fluctuation of the core MOS tube of the amplifier, so that the amplifier is stable in the whole frequency band under different process angles, preventing self-oscillation of the amplifier and generating unnecessary output frequency. The invention adopts the body electrode isolation technology to design the neutralizing capacitor of the MOS tube, cuts off the path introduced by the C _db and parasitic resistance of the neutralizing capacitor MOS tube, does not cause the loss of the differential output end, and thus has good gain performance. The body electrode of the present invention isolates a large resistance, can cut off the AC path from the body electrode to the ground potential, and suppress the parasitic resistance of the body electrode as a noise source to transmit thermal noise to the output end of the amplifier, thereby helping to improve the noise performance of the amplifier.

Second, considering the technical solution as a whole or from the product point of view, the technical effects and advantages of the technical solution to be protected by the present invention are specifically described as follows:

In the present invention, the body electrodes of the MOS transistors used as neutralizing capacitors are respectively connected to the ground with large resistances, which isolates the paths formed by C _db and parasitic resistances at both ends of the differential output of the amplifier, so the gain of the amplifier can be improved, and the noise coefficient of the amplifier can be optimized. , which helps to improve the overall performance of the RF chip. The present invention optimizes the gain and noise performance of the amplifier by connecting the bulk electrode of the MOS tube capacitor to the ground independently. The invention improves the original MOS tube neutralization capacitor technology, and isolates the loss of C _db and some parasitic resistances to the gain of the output end by connecting the body electrode of the neutralization capacitor MOS tube with a large resistance to the ground. thermal noise transmitted to the body electrode parasitic resistance of the output. Therefore, the amplifier of the present invention has better gain and noise performance. The MOS tube capacitor used in the present invention utilizes the consistency of the same MOS tube during processing, so it can follow the change of C _gd of the core MOS tube of the amplifier, so that under different process angles, the full frequency band of the amplifier is stable, and the influence of self-oscillation of the amplifier is prevented. working state and frequency of interference. From the viewpoints of gain, noise and stability, the amplifier scheme of the present invention is helpful for improving the overall performance of the radio frequency chip.

Third, as an auxiliary evidence of inventive step for the claims of the present invention, it is also reflected in the following important aspects:

(1) The expected income and commercial value after the technical solution of the present invention is transformed are: the present invention improves the stability of the amplifier against the process fluctuation resistance by improving the neutralization capacitor technology, and improves the yield of the product. Compared with the traditional MOS tube capacitor, the invention improves the noise coefficient and gain performance of the amplifier, so it can be applied to amplifier products such as high-performance low-noise amplifiers and driving amplifiers.

(2) the technical scheme of the present invention solves the technical problem that people have been eager to solve but have not been able to achieve success all the time:

In the design of traditional RF amplifiers, if metal capacitors are used as neutralizing capacitors, the process fluctuations of MOS tubes cannot be tracked, and stability problems are prone to occur; if traditional MOS tube neutralizing capacitor technology is used, although the stability is good, the gain and The noise figure will degrade, affecting the performance of the amplifier. The invention takes into account the gain and noise performance of the amplifier while ensuring the stability of the amplifier against process fluctuations.

Description of drawings

1 is a schematic structural diagram of a neutralizing capacitor amplifier with a body electrode isolation MOS tube provided by an embodiment of the present invention;

FIG. 2 is a circuit diagram of an amplifier with a body electrode-source short-connected MOS tube neutralizing capacitor provided by an embodiment of the present invention;

3 is a schematic diagram of a simulation situation of Gmax varying with frequency under different process angles provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of the comparison of the amplifier Gmax with frequency variation provided by an embodiment of the present invention;

5 is a schematic diagram of a comparison of NFmin with frequency variation of an amplifier provided in an embodiment of the present invention;

6 is a schematic diagram of the stability of an amplifier with a metal neutralization capacitor provided by an embodiment of the present invention under different process angles;

In the figure: 1. The first load; 2. The positive-phase output signal terminal Vout+; 3. The third MOS tube; 4. The positive-phase input signal terminal Vin+; 5. The first MOS tube; 6. The second resistor; 7. The first A resistor; 8, the third resistor; 9, the second MOS transistor; 10, the inverting input signal terminal Vin-; 11, the fourth MOS transistor; 12, the negative phase output signal terminal Vout-; 13, the second load.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

1. Explain the embodiment. In order for those skilled in the art to fully understand how the present invention is specifically implemented, this part is an explanatory embodiment to expand the description of the technical solutions of the claims.

As shown in FIG. 1 , the source electrode and the body electrode of the first MOS transistor 5 in the isolation MOS transistor with the body electrode provided by the embodiment of the present invention and the first MOS transistor 5 in the capacitor amplifier are grounded, and the gate of the first MOS transistor 5 is connected to the non-inverting input. Signal terminal Vin+4, the drain of the first MOS transistor 5 is connected to the non-inverting output signal terminal Vout+2; the source and body electrodes of the second MOS transistor 9 are grounded, and the gate of the second MOS transistor 9 is connected reversely The phase input signal terminal Vin-10, the drain in the second MOS transistor 9 is connected to the negative phase output signal terminal Vout-12; the source in the third MOS transistor 3 is connected with the first resistor 7, and the body in the third MOS transistor 3 is connected The electrode is connected to the second resistor 6, the gate of the third MOS transistor 3 is connected to the positive-phase input signal terminal Vin+4, and the drain of the third MOS transistor 3 is connected to the negative-phase output signal terminal Vout-12;

The source of the fourth MOS transistor 11 is connected to the first resistor 7, the body electrode of the fourth MOS transistor 11 is connected to the third resistor 8, the gate of the fourth MOS transistor 11 is connected to the inverting input signal terminal Vin-10, and the first The drain of the four MOS transistors 11 is connected to the positive phase output signal terminal Vout+2; the positive phase output signal terminal Vout+2 is connected to the first load 1, and the first load 1 is connected to the power supply Vdd; the negative phase output signal terminal Vout-12 The second load 13 is connected to the power supply Vdd; one end of the first resistor 7 is grounded, one end of the second resistor 6 is grounded, and one end of the third resistor 8 is grounded. The first MOS transistor 5 and the second MOS transistor 9 have the same size, the third MOS transistor 3 and the fourth MOS transistor 11 have the same size; the second resistor 6 and the third resistor 8 have the same size, the first resistor 7, The second resistor 6 and the third resistor 8 need to be in the order of kiloohms and above.

The working principle of the present invention is as follows: the first MOS transistor 5 and the second MOS transistor 9 are the core MOS transistors of the amplifier for amplifying signals, and the third MOS transistor 3 and the fourth MOS transistor 11 are neutralizing capacitor MOS transistors. When the value of the first resistor 7 is large, there is hardly any current passing through the third MOS transistor 3 and the fourth MOS transistor 11 , and the third MOS transistor 3 and the fourth MOS transistor 11 work in an almost off state. One end of C _gd of the third MOS transistor 3 and the first MOS transistor 5 are both connected to the positive-phase input signal terminal Vin+4, and the other ends are respectively connected to the negative-phase output signal terminal Vout-12 and the positive-phase output signal terminal Vout+2. On the contrary, they can cancel each other out, and similarly the C _gd of the fourth MOS transistor 11 and the second MOS transistor 9 can also cancel each other out. The body electrodes of the third MOS transistor 3 and the fourth MOS transistor 11 are respectively connected to the ground through the large second resistor 6 and the third resistor 8, so the DC potential of the body electrodes is the ground potential. The DC potentials of the drain and body electrodes of the first MOS transistor 5 , the second MOS transistor 9 , the third MOS transistor 3 and the fourth MOS transistor 11 are the same, and the depletion region between the drain and the body electrode is similar.

2. Application examples. In order to prove the creativity and technical value of the technical solution of the present invention, this part is an application example of the technical solution in the claims on specific products or related technologies.

Compared with the traditional MOS tube capacitor, the invention improves the noise coefficient and gain performance of the amplifier, so it can be applied to amplifier products such as high-performance low-noise amplifiers and driving amplifiers. It can be used in radio frequency chips, wireless communication chips, radar chips, etc.

3. Evidence of the relevant effects of the embodiment. The embodiments of the present invention have achieved some positive effects in the process of research and development or use, and indeed have great advantages compared with the prior art.

In the prior art, as shown in FIG. 2 , the body electrodes and source electrodes of M3 and M4 are shorted to one end of the large resistor R1, and the potential of the body electrodes is higher than the ground potential, so the drain electrodes of M3, M4 and M1, M2 are The depletion region is different between the body electrodes. And this depletion region has a great influence on the capacitor C _gd . Therefore, in the present invention, compared with the prior art, the C _gd of the core MOS transistor and the C _gd of the neutralizing capacitor MOS transistor have a more similar environment. The consistency is better, and it is more resistant to process fluctuations. As shown in Figure 3, the dimensions of M3 and M4 are designed according to the tt process angle, and the curve of the Gmax of the amplifier under the tt, ff and ss process angles as a function of frequency is simulated. Among them, the solid line is the tt process angle, the dotted line is the ff process angle, and the dashed line is the ss process angle. Comparing Figure 6 and Figure 3, it can be seen that under different process angles, the amplifier has no obvious turning point from MSG to MAG in the whole frequency band, and almost all are in the state of MAG, so it can be achieved under different process angles. Full-band stability. The body electrodes of M3 and M4 are connected to the ground through the large resistors R2 and R3. Therefore, the C _db and parasitic resistances of M3 and M4 cause the path to be cut off, which will not increase the loss of the output node. solution, the amplifier gain of the present invention is higher.

As shown in Figure 4, it is the case where the Gmax of the amplifier changes with frequency, in which the black solid line is the Gmax of the amplifier of the present invention, the gray dotted line is the Gmax of the amplifier with the body electrode-source short-circuiting scheme, the M1-2 size of the two schemes, The DC bias voltage is the same. It can be seen from FIG. 4 that the Gmax of the amplifier of the present invention is greater than the Gmax of the amplifier of the body electrode-source short circuit scheme at each frequency point. At 50 GHz, the Gmax of the present invention is 0.8dB higher than that of the prior art. At 90 GHz, The Gmax of the present invention is 5.01dB, and the Gmax of the prior art is 4.34dB, and the present invention is 0.67dB higher than the prior art. The large resistors R2 and R3 have a strong isolation effect. The thermal noise generated by the parasitic resistance of the body electrode will encounter a high-impedance loop, so it will not be superimposed on the output of the amplifier, so it can be compared to the body electrode and the source. scheme, has a lower noise figure. As shown in FIG. 5 , the black curve is the NFmin of the amplifier of the present invention, and the gray dotted line is the NFmin of the prior art amplifier. In the whole frequency band, the NFmin of the amplifier of the present invention is smaller than the NFmin of the prior art. At 50GHz, the NFmin of the present invention is 2.7662dB, the NFmin of the prior art is 2.9299dB, and the present invention is 0.1637dB lower than the prior art; at 100GHz, the NFmin of the present invention is 4.9113dB, and the NFmin of the prior art is 5.1738dB, The present invention is 0.2625dB lower than the prior art. The higher the frequency, the more noise the parasitic resistance at the body electrode in the prior art enters the output end through the path of capacitance such as C _db . Therefore, the higher the frequency, the more the present invention improves NFmin.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art is within the technical scope disclosed by the present invention, and all within the spirit and principle of the present invention Any modifications, equivalent replacements and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. The utility model provides a take body electrode to keep apart MOS pipe neutralization capacitor amplifier which characterized in that, take body electrode to keep apart MOS pipe neutralization capacitor amplifier and be provided with:

the MOS transistor comprises a first MOS transistor, a second MOS transistor, a third MOS transistor and a fourth MOS transistor;

the grid electrode in the first MOS tube is connected with a positive phase input signal end Vin +, and the drain electrode in the first MOS tube is connected with a positive phase output signal end Vout +; the grid electrode in the second MOS tube is connected with an inverting input signal end Vin-, and the drain electrode in the second MOS tube is connected with a negative phase output signal end Vout-;

a source electrode in the third MOS tube is connected with the first resistor, and a body electrode in the third MOS tube is connected with the second resistor; and a source electrode in the fourth MOS tube is connected with the first resistor, and a body electrode in the fourth MOS tube is connected with the third resistor.

2. The band body electrode isolated MOS transistor neutralization capacitor amplifier of claim 1 wherein the first MOS transistor is provided with a source electrode and a body electrode, the source electrode and the body electrode being grounded.

3. The band body electrode isolated MOS transistor neutralization capacitor amplifier of claim 1 wherein the second MOS transistor is provided with a source electrode and a body electrode, the source electrode and the body electrode being grounded.

4. The band electrode isolation MOS neutralizing capacitor amplifier as claimed in claim 1, wherein the third MOS transistor has a gate connected to the positive input signal terminal Vin +, and a drain connected to the negative output signal terminal Vout-.

5. The strap electrode isolation MOS neutralizing capacitor amplifier of claim 1 wherein the fourth MOS transistor has a gate connected to the inverting input signal terminal Vin-, and a drain connected to the non-inverting output signal terminal Vout +.

6. The strap electrode isolation MOS transistor neutralization capacitor amplifier of claim 1 wherein the non-inverting output signal terminal Vout + is connected to a first load, the first load being connected to a power supply Vdd.

7. The strap electrode isolation MOS transistor neutralizing capacitor amplifier of claim 1 wherein the negative phase output signal terminal Vout "is connected to a second load, the second load being connected to a power supply Vdd.

8. The MOS transistor neutralizing capacitor amplifier with body electrode isolation of claim 1 wherein one end of the first resistor is grounded, one end of the second resistor is grounded, and one end of the third resistor is grounded;

the first MOS tube and the second MOS tube have the same size, and the third MOS tube and the fourth MOS tube have the same size;

the second resistor and the third resistor have the same size, and the values of the first resistor, the second resistor and the third resistor are in the order of kilo-ohm or above.

9. A wireless communication terminal, characterized in that the wireless communication terminal is provided with the strip body electrode isolation MOS transistor neutralization capacitive amplifier of any one of claims 1 to 8.

10. A radio frequency chip, wherein the radio frequency chip comprises the MOS transistor neutralizing capacitor amplifier with strip electrode isolation according to any one of claims 1 to 8.

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