Noise elimination broadband low-noise amplifier without auxiliary amplifier

Abstract

A noise elimination broadband low-noise amplifier without an auxiliary amplifier comprises an input matching network, a first-stage amplification module, an inter-stage matching network, a second-stage amplification module and an output matching module which are sequentially cascaded. The transformer is added to the gate end and the source end of the differential common-gate amplifier, so that noise elimination is realized without introducing an additional auxiliary amplifier. The influence of the parasitic capacitance of the transistor is weakened by introducing the neutralizing capacitor, so that the noise elimination technology can be realized at high frequency. By setting a proper inter-stage matching network and a load inductance value, the two-stage amplification module works at different center frequencies, so that a large bandwidth is kept while excessive gain is not lost. The two problems that firstly, noise generated by an auxiliary amplifier introduced for eliminating the noise of a main amplifier is difficult to eliminate, and secondly, the noise elimination technology is difficult to take effect under high frequency due to parasitic capacitance of a transistor are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency integrated circuits, and in particular relates to a noise-cancelling broadband low-noise amplifier without an auxiliary amplifier. Background Art

[0002] In modern communications systems, the low-noise amplifier (LNA) is a key component in the receiver front end. Its function is to amplify weak signals while simultaneously introducing minimal noise to improve the signal-to-noise ratio (SNR) of the entire receiver system. Therefore, the performance of the LNA directly impacts the signal quality and noise level of the entire system. Traditional LNA designs often face a trade-off between bandwidth and noise. To overcome this challenge, researchers have proposed noise cancellation techniques.

[0003] Traditional low-noise amplifiers based on noise cancellation technology typically consist of a main amplifier and an auxiliary amplifier. The main amplifier often uses a common-gate amplifier with good bandwidth characteristics, but common-gate amplifiers suffer from high noise figures and low gain. Therefore, an auxiliary amplifier is introduced to offset the noise generated by the main amplifier while providing a certain amount of gain. However, this structure only cancels the noise generated by the main amplifier; the newly introduced auxiliary amplifier generates additional noise, making the noise cancellation incomplete.

[0004] In related technologies, Sun Jingye's patent application, "Differential Low-Noise Amplifier and Noise Cancellation Method Based on Dual-Path Noise Cancellation" (Application No. CN202311093978.2, Publication No. CN117060860A, Publication Date 2023.11.14), uses a dual-path differential noise cancellation structure to completely or partially cancel the noise generated by multiple devices in a low-noise amplifier. However, as the operating frequency increases, the parasitic capacitance of the transistor itself will cause the bandwidth and noise performance of the overall circuit to deteriorate, making the noise cancellation technology ineffective at high frequencies.

[0005] In summary, existing noise cancellation technology has two problems: first, the noise generated by the auxiliary amplifier introduced to eliminate the noise of the main amplifier is difficult to eliminate; second, the parasitic capacitance of the transistor itself makes noise cancellation technology difficult to be effective at high frequencies. Summary of the Invention

[0006] Taking into account the problems existing in the above-mentioned prior art, the present invention provides a noise-canceling broadband low-noise amplifier without an auxiliary amplifier, so as to solve the problems existing in the existing traditional noise-canceling low-noise amplifier, that is, the noise generated by the auxiliary amplifier itself introduced to eliminate the noise of the main amplifier is difficult to eliminate, and the parasitic capacitance of the transistor itself makes the noise cancellation technology ineffective at high frequencies, thereby affecting its overall performance.

[0007] In order to solve the above problems, the present invention adopts the following technical solutions:

[0008] A noise-canceling broadband low-noise amplifier without an auxiliary amplifier comprises an input matching network, a first-stage amplification module, an inter-stage matching network, a second-stage amplification module and an output matching module which are cascaded in sequence;

[0009] The input matching network, the inter-stage matching network, and the output matching network are used to achieve impedance matching; wherein the input matching network is connected to the RF signal input terminal, and the output matching network is connected to the RF signal output terminal;

[0010] The first-stage amplifier module includes NMOS transistors M1 and M2, inductors L2, L3, L4, L6, L7, L8, L9, L10, L12 and L13, and capacitors C3 and C4. At the same time, inductors L2 and L7 and inductors L3 and L6 are coupled to form two transformers, and their coupling coefficients are K1 and K2 respectively.

[0011] Among them, the NMOS transistor M1 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L3, whose source is connected to one end of the inductor L4 and one end of the capacitor C3, and whose drain is connected to one end of the inductor L9 and one end of the capacitor C4; the NMOS transistor M2 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L7, whose source is connected to one end of the inductor L8 and the other end of the capacitor C4, and whose drain is connected to one end of the inductor L12 and the other end of the capacitor C3; one end of the inductor L2 is grounded, and the other end is connected to the other end of the inductor L4; the other end of the inductor L4 is also connected to the positive electrode of the output end of the input matching network, serving as the positive electrode of the input end of the first stage amplifier module; one end of the inductor L6 is grounded, and the other end is connected Connect to the other end of inductor L8; the other end of inductor L8 is also connected to the negative electrode of the output end of the input matching network, serving as the negative electrode of the input end of the first-stage amplifier module; the other end of inductor L9 is connected to inductor L10 and the positive electrode of the input end of the interstage matching network, serving as the positive electrode of the output end of the first-stage amplifier circuit; the other end of inductor L10 is connected to the power supply voltage VDD; the other end of inductor L12 is connected to inductor L13 and the negative electrode of the input end of the interstage matching network, serving as the negative electrode of the output end of the first-stage amplifier circuit; the other end of inductor L13 is connected to the power supply voltage VDD; inductor L2 is used as the main coil, and inductor L7 is used as the secondary coil to form a transformer, whose coupling coefficient is K1; inductor L6 is used as the main coil, and inductor L3 is used as the secondary coil to form a transformer, whose coupling coefficient is K2.

[0012] Furthermore, the input matching network includes capacitors C1, C2 and inductors L1, L5; one end of capacitor C1 is connected to the positive pole of the RF signal input, serving as the positive pole of the input matching network input, and the other end is connected to one end of the inductor L1; one end of capacitor C2 is connected to the negative pole of the RF signal input, serving as the negative pole of the input matching network input, and the other end is connected to one end of the inductor L5; the other end of the inductor L1 is connected to the positive pole of the input end of the first-stage amplification module, serving as the positive pole of the output end of the input matching network; the other end of the inductor L5 is connected to the negative pole of the input end of the first-stage amplification module, serving as the negative pole of the output end of the input matching network.

[0013] Furthermore, the inter-stage matching network includes inductors L11, L14 and capacitors C5, C6; one end of the inductor L11 is connected to the positive electrode of the output end of the first-stage amplification module, serving as the positive electrode of the input end of the inter-stage matching network, and the other end is connected to the capacitor C5; one end of the inductor L14 is connected to the negative electrode of the output end of the first-stage amplification module, serving as the negative electrode of the input end of the inter-stage matching network, and the other end is connected to the capacitor C6; the other end of the capacitor C5 is connected to the positive electrode of the input end of the second-stage amplification module, serving as the positive electrode of the output end of the inter-stage matching network; the other end of the capacitor C6 is connected to the negative electrode of the input end of the second-stage amplification module, serving as the negative electrode of the output end of the inter-stage matching network.

[0014] Furthermore, the second-stage amplification module includes NMOS transistors M3 and M4, inductors L15, L16, L17, L18, L19, L20, L21, L22, L24 and L25, and capacitors C7 and C8. At the same time, the inductors L15 and L19 and the inductors L16 and L18 are coupled to form two transformers, and their coupling coefficients are K3 and K4 respectively.

[0015] Among them, the NMOS transistor M3 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L16, whose source is connected to one end of the inductor L17 and one end of the capacitor C7, and whose drain is connected to one end of the inductor L21 and one end of the capacitor C8; the NMOS transistor M4 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L19, whose source is connected to one end of the inductor L20 and the other end of the capacitor C8, and whose drain is connected to one end of the inductor L24 and the other end of the capacitor C7; one end of the inductor L15 is grounded, and the other end is connected to the other end of the inductor L17; the other end of the inductor L17 is also connected to the positive electrode of the output end of the inter-stage matching network, serving as the positive electrode of the input end of the second-stage amplifier module; one end of the inductor L18 is grounded, and the other end Connect the other end of inductor L20; the other end of inductor L20 is also connected to the negative electrode of the output end of the inter-stage matching network, serving as the negative electrode of the input end of the second-stage amplification module; the other end of inductor L21 is connected to inductor L22 and the positive electrode of the input end of the output matching network, serving as the positive electrode of the output end of the second-stage amplification circuit; the other end of inductor L22 is connected to the power supply voltage VDD; the other end of inductor L24 is connected to inductor L25 and the negative electrode of the input end of the output matching network, serving as the negative electrode of the output end of the second-stage amplification circuit; the other end of inductor L25 is connected to the power supply voltage VDD; inductor L15 serves as the main coil, and inductor L19 serves as the secondary coil to form a transformer, whose coupling coefficient is K3; inductor L18 serves as the main coil, and inductor L16 serves as the secondary coil to form a transformer, whose coupling coefficient is K4.

[0016] Furthermore, the output matching network consists of inductors L23, L26 and capacitors C9, C10; one end of the inductor L23 is connected to the positive electrode of the output end of the second-stage amplification module, serving as the positive electrode of the input end of the output matching network, and the other end is connected to one end of the capacitor C9; one end of the inductor L26 is connected to the negative electrode of the output end of the second-stage amplification module, serving as the negative electrode of the input end of the output matching network, and the other end is connected to one end of the capacitor C9; the other end of the capacitor C9 is connected to the positive electrode of the RF signal output, serving as the positive electrode of the output end of the output matching network; the other end of the capacitor C10 is connected to the negative electrode of the RF signal output, serving as the negative electrode of the output end of the output matching network.

[0017] Furthermore, the value of the bias voltage Vb is 0.7V, and the value of the power supply voltage VDD is 0.9V.

[0018] The present invention provides a noise-eliminating broadband low-noise amplifier without an auxiliary amplifier. The two-stage amplification module used adopts a differential common-gate amplifier. By adding a transformer between the gate and source poles of the two NMOS tubes, that is, making the differential pair tubes become common-source amplifiers, and by reasonably setting the parameters of the transformer, it is possible to achieve noise elimination technology without introducing an additional auxiliary amplifier; at the same time, due to the use of a differential common-gate amplifier, compared with the traditional single-ended noise-eliminating low-noise amplifier, the influence of the parasitic capacitance of the transistor itself is weakened by adding a neutralizing capacitor, so that the noise elimination technology can also be achieved at high frequencies. On this basis, each stage of the amplification module can achieve a very large bandwidth. Combined with the interleaved tuning technology, the center frequencies of the two-stage amplification modules are set at different frequency points, so that the overall gain is significantly improved while ensuring that the bandwidth is not significantly reduced. Finally, by setting appropriate input and output and inter-stage matching networks, suitable circuit performance parameters are obtained.

[0019] Compared with the prior art, the novel broadband low-noise amplifier based on the noise cancellation technology of the present invention has better comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a low-noise amplifier that uses a traditional common-source-common-gate structure for noise elimination.

[0021] Figure 2 This is a schematic diagram of a noise cancellation technology implemented by a noise-canceling broadband low-noise amplifier without an auxiliary amplifier provided in an embodiment.

[0022] Figure 3 A circuit schematic diagram of a noise-canceling broadband low-noise amplifier without an auxiliary amplifier provided in an embodiment.

[0023] Figure 4 A circuit schematic diagram of a noise-canceling broadband low-noise amplifier with an auxiliary amplifier provided in an embodiment.

[0024] Figure 5 This is a diagram showing simulation results of the gain of a noise-canceling broadband low-noise amplifier without an auxiliary amplifier provided in an embodiment.

[0025] Figure 6 This is a diagram showing simulation results of input matching of a noise-canceling broadband low-noise amplifier without an auxiliary amplifier provided in an embodiment.

[0026] Figure 7 This is a diagram showing simulation results of output matching of a noise-canceling broadband low-noise amplifier without an auxiliary amplifier provided in an embodiment.

[0027] Figure 8Graph showing simulation results of the noise figures of the noise-canceling broadband low-noise amplifiers with and without an auxiliary amplifier provided in the embodiment.

[0028] Reference numerals:

[0029] 1. Input matching network, 2. First stage amplifier module, 3. Interstage matching network, 4. Second stage amplifier module, 5. Output matching network, 6. First stage auxiliary amplifier, 7. Second stage auxiliary amplifier. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention and not all of them. Based on the embodiments of the present invention, those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and do not limit the scope of protection of the present invention.

[0031] This embodiment provides a noise-canceling broadband low-noise amplifier without an auxiliary amplifier. For its specific structure, please refer to Figure 3 The principle of noise elimination technology implemented by the present invention can be found in Figure 2 Taking the first-stage amplifier module as an example, the primary source of noise is the channel noise current generated by the two NMOS transistors. For symmetry reasons, the channel noise current source of transistor M2 will be specifically analyzed. Since transistor M2 uses a common-gate connection, the noise current generated by this noise current source produces noise voltages of opposite phases at its source and drain. However, the input signal voltage to be amplified is in phase after amplification by the common-gate transistor. By adding inductor L6 to the source of transistor M2 and inductor L3 to the gate of transistor M1 to form a transformer with a coupling coefficient of K2, a signal voltage and noise voltage with the same phase as those at the source of transistor M2 are generated at the gate of transistor M1. In this case, transistor M1 can be considered a common-source amplifier with a signal input at the gate. After amplification by transistor M1, the signal voltage and noise voltage have opposite phases. Therefore, the signal voltage at the drain of transistor M1 is in opposite phase to the voltage at the drain of transistor M2, while the noise voltage at the drain of transistor M1 is in phase with the noise voltage at the drain of transistor M2. Because the amplifier module uses a differential output, the signal voltage is amplified while the noise voltage cancels each other out, thus achieving noise cancellation without introducing an additional auxiliary amplifier. At the same time, due to the use of a differential structure, capacitors C3 and C4 can be added as neutralizing capacitors, thereby reducing the influence of the parasitic capacitance between the gate and drain of the transistor itself, allowing the noise cancellation technology to be effective at high frequencies, thereby increasing the bandwidth of the amplifier module. For comparison, a noise-canceling broadband low-noise amplifier with an auxiliary amplifier is shown. For its specific structure, see [ 1 ]. Figure 4This low-noise amplifier achieves noise cancellation based on the same principle as the traditional cascode structure. The auxiliary amplifier, consisting of a differential common-source amplifier, receives its input signal from a transformer at the source of the main amplifier, while its output signal is coupled to the drain of the main amplifier via the transformer. By setting appropriate NMOS transistor parameters and load, the main amplifier's noise can be eliminated.

[0032] The two-stage amplifier modules used in this example are both common-gate amplifiers, with a single-pole gain of approximately 7dB and a bandwidth of approximately 40GHz. If the two-stage amplifiers are simply cascaded and the same structure is maintained, the bandwidth of the multi-stage amplifier will be smaller than that of the single-stage amplifier. The main reason for this is that when single-stage amplifiers are cascaded, since the S21 response characteristic is high in the middle and low on both sides, the cascade process directly adds S21. This process makes the S21 frequency response curve sharper, and the S21 on both sides of the center frequency decreases faster, making the 3dB bandwidth of the two-stage amplifier smaller than the 3dB bandwidth of the single-stage amplifier. Therefore, this example sets appropriate inter-stage matching networks and load inductance values to allow the two-stage amplifier modules to operate at different center frequencies, that is, interleaved tuning technology, thereby maintaining a large bandwidth without losing too much gain.

[0033] The new broadband low-noise amplifier based on noise cancellation technology in the above example is simulated and verified:

[0034] The simulation conditions are within the range of 60GHz~120GHz, using TSMC28nm CMOS process, a power supply voltage of 0.9V, a gate bias voltage of 0.7V, and circuit simulation using the Cadence simulation tool.

[0035] Simulation results refer to Figures 5 to 8 This example achieves a maximum gain of 11dB at 80GHz and 98GHz, and the gain flatness within this range is less than 0.5dB. The 3dB bandwidth covers 71GHz~107GHz. Its input matching performance S11 is less than -17dB in the range of 80GHz~98GHz, and its output matching performance S22 is less than -14dB in the range of 80GHz~98GHz, showing good input and output matching. Its noise figure is less than 5.3dB in the range of 71GHz~107GHz, with the lowest noise figure being 4.6dB at 80GHz. The noise flatness is less than 0.6dB in the range of 71GHz~107GHz. Compared with the traditional noise-canceling broadband low-noise amplifier with auxiliary amplifier, its noise figure is significantly reduced. In summary, the new broadband low-noise amplifier based on noise cancellation technology provided by this example has good bandwidth performance and can also achieve good noise performance in a wider bandwidth.

[0036] The above embodiments are only a part of the embodiments of the present invention and not all of them. For those skilled in the art, several simple replacements and deductions made without departing from the concept of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A noise-canceling broadband low-noise amplifier without an auxiliary amplifier, comprising an input matching network, a first-stage amplification module, an inter-stage matching network, a second-stage amplification module, and an output matching module connected in cascade order, characterized in that: The input matching network, the inter-stage matching network, and the output matching network are used to achieve impedance matching; wherein the input matching network is connected to the RF signal input terminal, and the output matching network is connected to the RF signal output terminal; The first-stage amplifier module includes NMOS transistors M1 and M2, inductors L2, L3, L4, L6, L7, L8, L9, L10, L12 and L13, and capacitors C3 and C4. At the same time, inductors L2 and L7 and inductors L3 and L6 are coupled to form two transformers, and their coupling coefficients are K1 and K2 respectively. Among them, the NMOS transistor M1 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L3, whose source is connected to one end of the inductor L4 and one end of the capacitor C3, and whose drain is connected to one end of the inductor L9 and one end of the capacitor C4; the NMOS transistor M2 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L7, whose source is connected to one end of the inductor L8 and the other end of the capacitor C4, and whose drain is connected to one end of the inductor L12 and the other end of the capacitor C3; one end of the inductor L2 is grounded, and the other end is connected to the other end of the inductor L4; the other end of the inductor L4 is also connected to the positive electrode of the output end of the input matching network, serving as the positive electrode of the input end of the first stage amplifier module; one end of the inductor L6 is grounded, and the other end is connected Connect to the other end of inductor L8; the other end of inductor L8 is also connected to the negative electrode of the output end of the input matching network, serving as the negative electrode of the input end of the first-stage amplifier module; the other end of inductor L9 is connected to inductor L10 and the positive electrode of the input end of the interstage matching network, serving as the positive electrode of the output end of the first-stage amplifier circuit; the other end of inductor L10 is connected to the power supply voltage VDD; the other end of inductor L12 is connected to inductor L13 and the negative electrode of the input end of the interstage matching network, serving as the negative electrode of the output end of the first-stage amplifier circuit; the other end of inductor L13 is connected to the power supply voltage VDD; inductor L2 is used as the main coil, and inductor L7 is used as the secondary coil to form a transformer, whose coupling coefficient is K1; inductor L6 is used as the main coil, and inductor L3 is used as the secondary coil to form a transformer, whose coupling coefficient is K2.

2. The noise-canceling broadband low-noise amplifier without an auxiliary amplifier according to claim 1, characterized in that: The input matching network includes capacitors C1, C2 and inductors L1, L5; One end of capacitor C1 is connected to the positive electrode of the RF signal input, serving as the positive electrode of the input matching network input, and the other end is connected to one end of inductor L1; one end of capacitor C2 is connected to the negative electrode of the RF signal input, serving as the negative electrode of the input matching network input, and the other end is connected to one end of inductor L5; the other end of inductor L1 is connected to the positive electrode of the input end of the first-stage amplification module, serving as the positive electrode of the output end of the input matching network; the other end of inductor L5 is connected to the negative electrode of the input end of the first-stage amplification module, serving as the negative electrode of the output end of the input matching network.

3. The noise-canceling broadband low-noise amplifier without an auxiliary amplifier according to claim 1, characterized in that: The inter-stage matching network includes inductors L11, L14 and capacitors C5, C6; One end of the inductor L11 is connected to the positive electrode of the output end of the first-stage amplification module, serving as the positive electrode of the input end of the inter-stage matching network, and the other end is connected to the capacitor C5; one end of the inductor L14 is connected to the negative electrode of the output end of the first-stage amplification module, serving as the negative electrode of the input end of the inter-stage matching network, and the other end is connected to the capacitor C6; the other end of the capacitor C5 is connected to the positive electrode of the input end of the second-stage amplification module, serving as the positive electrode of the output end of the inter-stage matching network; the other end of the capacitor C6 is connected to the negative electrode of the input end of the second-stage amplification module, serving as the negative electrode of the output end of the inter-stage matching network.

4. The noise-canceling broadband low-noise amplifier without an auxiliary amplifier according to claim 1, characterized in that: The second-stage amplifier module includes NMOS transistors M3 and M4, inductors L15, L16, L17, L18, L19, L20, L21, L22, L24 and L25, and capacitors C7 and C8. At the same time, the inductors L15 and L19 and the inductors L16 and L18 are coupled to form two transformers, and their coupling coefficients are K3 and K4 respectively. Among them, the NMOS transistor M3 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L16, whose source is connected to one end of the inductor L17 and one end of the capacitor C7, and whose drain is connected to one end of the inductor L21 and one end of the capacitor C8; the NMOS transistor M4 adopts a common gate connection method to form a common gate amplifier, whose gate is connected to the bias voltage Vb through the inductor L19, whose source is connected to one end of the inductor L20 and the other end of the capacitor C8, and whose drain is connected to one end of the inductor L24 and the other end of the capacitor C7; one end of the inductor L15 is grounded, and the other end is connected to the other end of the inductor L17; the other end of the inductor L17 is also connected to the positive electrode of the output end of the inter-stage matching network, serving as the positive electrode of the input end of the second-stage amplifier module; one end of the inductor L18 is grounded, and the other end Connect the other end of inductor L20; the other end of inductor L20 is also connected to the negative electrode of the output end of the inter-stage matching network, serving as the negative electrode of the input end of the second-stage amplification module; the other end of inductor L21 is connected to inductor L22 and the positive electrode of the input end of the output matching network, serving as the positive electrode of the output end of the second-stage amplification circuit; the other end of inductor L22 is connected to the power supply voltage VDD; the other end of inductor L24 is connected to inductor L25 and the negative electrode of the input end of the output matching network, serving as the negative electrode of the output end of the second-stage amplification circuit; the other end of inductor L25 is connected to the power supply voltage VDD; inductor L15 serves as the main coil, and inductor L19 serves as the secondary coil to form a transformer, whose coupling coefficient is K3; inductor L18 serves as the main coil, and inductor L16 serves as the secondary coil to form a transformer, whose coupling coefficient is K4.

5. The noise-canceling broadband low-noise amplifier without an auxiliary amplifier according to claim 1, characterized in that: The output matching network consists of inductors L23, L26 and capacitors C9, C10; One end of the inductor L23 is connected to the positive electrode of the output end of the second-stage amplification module, serving as the positive electrode of the input end of the output matching network, and the other end is connected to one end of the capacitor C9; one end of the inductor L26 is connected to the negative electrode of the output end of the second-stage amplification module, serving as the negative electrode of the input end of the output matching network, and the other end is connected to one end of the capacitor C9; the other end of the capacitor C9 is connected to the positive electrode of the RF signal output, serving as the positive electrode of the output end of the output matching network; the other end of the capacitor C10 is connected to the negative electrode of the RF signal output, serving as the negative electrode of the output end of the output matching network.

6. The noise-canceling broadband low-noise amplifier without an auxiliary amplifier according to claim 1, characterized in that: The bias voltage Vb is 0.7V, and the power supply voltage VDD is 0.9V.

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