A negative control positive and negative voltage bias circuit and power amplifier protection circuit

Abstract

The present invention provides a negative-controlled positive and negative voltage bias circuit and a power amplifier protection circuit, which belong to the technical field of power amplifiers. The present invention integrates a negative voltage bias circuit with a negative control positive function, and samples the negative power supply voltage and the negative voltage bias output voltage at the same time. When the negative power supply and the negative voltage bias are both powered on, a power-on protection signal is generated. The trigger unit generates a start signal based on the power-on protection signal, and then controls the drain modulation module to turn on, ensuring that the gate voltage modulation is fully turned on before the drain voltage modulation is turned on, so as to ensure that the power-on sequence of the power amplifier is gate first and then drain, thereby avoiding burning the power amplifier. When either the negative power supply or the negative voltage bias loses power, a power-off protection signal is generated. The trigger unit generates a shutdown signal based on the power-off protection signal, and then controls the drain modulation module to turn off. When an abnormal power-off occurs in the gate voltage modulation, the drain power modulation is turned off to avoid burning the power amplifier, thereby improving the safety of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of power amplifiers, and in particular to a negative-controlled positive and negative voltage bias circuit and a power amplifier protection circuit. Background Art

[0002] Radar (radio detection and ranging) is a high-tech system that embodies the achievements of modern electronic science and technology. With the increase in various civilian needs and the rapid advancement of science and technology, the system, theory, method, technology and application of Radar technology have made great progress. Various new radar systems have emerged. Active phased array Radar has been widely used due to its multi-functionality, multi-target, high data, high precision and anti-clutter characteristics. T / R components are the core components of Radar systems and have also been greatly developed with the development of Radar technology.

[0003] The power amplifier is the core component of the radar transceiver (T / R) assembly. In the power amplifier modulation unit, the drain power modulation circuit and the gate modulation circuit are indispensable.

[0004] Traditional drain power modulation circuits consist of a drain driver circuit and power MOSFETs. They control the power amplifier to achieve modulation drive, negative control to positive, and discharge. They employ a half-bridge driver architecture to drive the high- and low-side MOSFETs into time-sharing operation. The negative control to positive function is integrated into the drain power modulation circuit, and a delay is applied to the drain power modulation enable port. After the negative power supply is turned on, the drain power modulation circuit is enabled within a fixed timeframe to implement power-on sequence protection for the power devices. However, a fixed delay that is too long can affect the timing control of the power amplifier, making it less practical. A fixed delay that is too short can prevent the negative voltage from being established at the gate port, potentially damaging the power amplifier or the drain modulation components, resulting in poor safety. Summary of the Invention

[0005] The embodiments of the present invention provide a negative-controlled positive-negative voltage bias circuit and a power amplifier protection circuit to solve the problems of poor applicability and poor safety of the existing fixed-delay negative-controlled positive mode.

[0006] In a first aspect, an embodiment of the present invention provides a negative-controlled positive-negative voltage bias circuit, comprising: a negative voltage bias module and a negative-controlled positive module;

[0007] The negative voltage bias module includes a negative voltage bias unit; the input end of the negative voltage bias unit is used to connect to a negative power supply, and the output end is used to output a negative voltage bias to the gate of the power amplifier;

[0008] The negative-to-positive module includes a power-on protection unit, a power-off protection unit, and a trigger unit;

[0009] The power-on protection unit outputs a power-on protection signal when both the negative power supply and the negative voltage bias are powered on;

[0010] The power-off protection unit outputs a power-off protection signal when at least one of the negative power supply or the negative voltage bias is powered off;

[0011] The trigger unit outputs a drain modulation module start signal based on the power-on protection signal, or outputs a drain modulation module shut-down signal based on the power-off protection signal, wherein the drain modulation module is used to modulate the drain of the power amplifier.

[0012] In a possible implementation, the negative voltage bias module further includes a reference voltage unit and a negative voltage bias sampling unit; the reference voltage unit outputs a negative power supply reference voltage, a negative voltage bias power-on reference voltage, and a negative voltage bias power-off reference voltage; the negative voltage bias sampling unit outputs a negative voltage bias sampling voltage;

[0013] The negative-to-positive module further includes a negative power sampling unit; the negative power sampling unit outputs a negative power sampling voltage; the negative power sampling unit includes a first negative power sampling unit and a second negative power sampling unit;

[0014] The power-on protection unit includes a first power-on unit and a second power-on unit; the reference voltage unit and the first negative power sampling unit are connected to the first power-on unit, and the first power-on unit determines that the negative power supply is powered on when the negative power supply sampling voltage is less than the negative power supply reference voltage; the reference voltage unit and the negative voltage bias sampling unit are connected to the second power-on unit, and the second power-on unit determines that the negative voltage bias is powered on when the negative voltage bias sampling voltage is less than the negative voltage bias power-on reference voltage;

[0015] The power-off protection unit includes a first power-off unit and a second power-off unit; the reference voltage unit and the second negative power supply sampling unit are connected to the first power-off unit, and the first power-off unit determines that the negative power supply is powered off when the negative power supply sampling voltage is greater than or equal to the negative power supply reference voltage; the reference voltage unit and the negative voltage bias sampling unit are connected to the second power-off unit, and the second power-off unit determines that the negative voltage bias is powered off when the negative voltage bias sampling voltage is greater than or equal to the negative voltage bias power-off reference voltage.

[0016] In a possible implementation, the power-on protection unit further includes a power-on signal determination unit;

[0017] The power-on signal judgment unit includes a first NOR gate and a first inverter; the first input end of the first NOR gate is connected to the output end of the first power-on unit, the second input end is connected to the output end of the second power-on unit, and the output end is connected to the input end of the first inverter; the output end of the first inverter outputs a power-on protection signal;

[0018] The power-off protection unit further includes a power-off signal judgment unit;

[0019] The power-off signal judgment unit includes a second inverter, a third inverter and a second NOR gate; the input end of the second inverter is connected to the output end of the first power-off unit, and the output end is connected to the first input end of the second NOR gate; the input end of the third inverter is connected to the output end of the second power-off unit, and the output end is connected to the second input end of the second NOR gate; the output end of the second NOR gate outputs a power-off protection signal.

[0020] In a possible implementation, the trigger unit includes an RS trigger and a level shift unit:

[0021] The R end of the RS trigger is connected to the output end of the power-on protection unit, the S end is connected to the output end of the power-off protection unit, and the output end is connected to the level shifting unit;

[0022] The level shift unit converts the negative level signal output by the RS trigger into a positive level signal, wherein a high level in the positive level signal indicates a drain modulation module on signal, and a low level indicates a drain modulation module off signal.

[0023] In a possible implementation, the level shifting unit is further connected to a negative power supply and a drain power supply of a drain modulation module;

[0024] The level shift unit outputs a drain modulation module shutdown signal when the drain power supply is not fully powered on.

[0025] In a possible implementation, the negative voltage bias unit includes an operational amplifier OP1, an adjustment tube, a resistor RADJ, and a resistor R1;

[0026] The negative terminal of the operational amplifier OP1 is input with a reference voltage, and the output terminal is connected to the gate of the adjustment tube;

[0027] The drain of the adjustment tube is connected to a negative power supply, and the source is connected to a resistor RADJ; the source serves as an output end for outputting a negative voltage bias to the gate of the power amplifier;

[0028] The resistor RADJ is connected in series with the resistor R1; one end of the resistor R1 away from the resistor RADJ is grounded;

[0029] A common terminal of the resistor RADJ and the resistor R1 is connected to the positive terminal of the operational amplifier OP1 and is also connected to the input terminal of the negative voltage bias sampling unit.

[0030] In a possible implementation, the reference voltage unit includes a bandgap reference voltage source, an operational amplifier OP2, a transistor MP1, and a resistor voltage divider unit;

[0031] The bandgap reference voltage source is connected to the positive terminal of the operational amplifier OP2; the output terminal of the operational amplifier OP2 is connected to the gate of the transistor MP1;

[0032] The source of the transistor MP1 is connected to a negative power supply, the drain is connected to the negative terminal of the operational amplifier OP2, and the drain is also connected to the input terminal of the resistor voltage divider unit;

[0033] The first port of the resistor voltage divider unit outputs a negative power supply reference voltage, the second port outputs a negative voltage bias power-on reference voltage, and the third port outputs a negative voltage bias power-off reference voltage.

[0034] In a possible implementation, the negative voltage bias sampling unit includes an operational amplifier OP3, a transistor MP2, a resistor R21, and a resistor R22;

[0035] The positive terminal of the operational amplifier OP3 is connected to the output terminal of the negative voltage bias unit, and the output terminal is connected to the gate of the transistor MP2;

[0036] The source of the transistor MP2 is connected to the negative power supply, and the drain is connected to the input end of the resistor R21, wherein the resistor R21 and the resistor R22 are connected in series, and the end of the resistor R22 away from the resistor R21 is grounded;

[0037] The common terminal of the resistor R21 and the resistor R22 is connected to the negative terminal of the operational amplifier OP3; the common terminal of the drain of the transistor MP2 and the resistor R21 serves as the output terminal of the negative bias sampling voltage.

[0038] In a possible implementation, the first negative power sampling unit includes a resistor R31 and a resistor R32;

[0039] The input end of the resistor R31 is connected to the negative power supply, and the output end is connected to the resistor R32;

[0040] One end of the resistor R32 away from the resistor R31 is grounded;

[0041] A common terminal of the resistor R31 and the resistor R32 serves as an output terminal of the first negative power supply sampling voltage.

[0042] In a second aspect, an embodiment of the present invention provides a power amplifier protection circuit, comprising a negative-controlled positive and negative voltage bias circuit as described in any one of the possible implementations above.

[0043] The embodiment of the present invention provides a negative-controlled positive and negative voltage bias circuit and a power amplifier protection circuit. The embodiment of the present invention integrates a negative voltage bias circuit with a negative control positive function, and samples the negative power supply voltage and the negative voltage bias output voltage at the same time. When the negative power supply and the negative voltage bias are both powered on, a power-on protection signal is generated. The trigger unit generates a start signal based on the power-on protection signal, and then controls the drain modulation module to turn on, ensuring that the gate voltage modulation is fully turned on before the drain voltage modulation is turned on, so as to ensure that the power-on sequence of the power amplifier is gate first and then drain, thereby avoiding burning the power amplifier. When either the negative power supply or the negative voltage bias loses power, a power-off protection signal is generated. The trigger unit generates a shutdown signal based on the power-off protection signal, and then controls the drain modulation module to turn off. When an abnormal power-off occurs in the gate voltage modulation, the drain power modulation is turned off to avoid burning the power amplifier, thereby improving the safety of the system. At the same time, the embodiment of the present invention avoids the use of a fixed delay method, is applicable to different power amplifier control timings, and has improved applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0045] Figure 1 This is a schematic structural diagram of a negative-control-positive method provided by an embodiment of the present invention;

[0046] Figure 2 Schematic diagram of an application scenario of a negative-controlled positive and negative voltage bias circuit provided by an embodiment of the present invention;

[0047] Figure 3 1 is a schematic structural diagram of a negative-controlled positive and negative voltage bias circuit provided by an embodiment of the present invention;

[0048] Figure 4 Schematic diagram of the structure of the negative-control-positive module provided by an embodiment of the present invention;

[0049] Figure 5 1 is a schematic structural diagram of a negative pressure bias module provided in an embodiment of the present invention;

[0050] Figure 6 is a schematic structural diagram of a reference voltage unit provided by an embodiment of the present invention;

[0051] Figure 7 is a structural diagram of a negative pressure bias sampling unit provided in an embodiment of the present invention;

[0052] Figure 8 It is a structural diagram of a level shifting unit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To help those skilled in the art better understand this solution, the following will clearly describe the technical solutions in the embodiments of this solution in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of this solution, not all of it. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of this solution.

[0054] Throughout the specification, claims, and accompanying figures of this solution, the term "including" and any variations thereof mean "including, but not limited to," and are intended to cover non-exclusive inclusions and are not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish between different objects, not to describe a specific order.

[0055] The following is a detailed description of the implementation of the present invention with reference to the accompanying drawings:

[0056] Power amplifiers (PAs) require peripheral modulation circuits, such as drain modulation and gate modulation. For example, gate modulation controls the on and off switching of the PA gate. Since the PA is a depletion-mode device, it uses a negative voltage generated by a negative bias to control the PA's source and drain currents.

[0057] In the power amplifier modulation unit, in addition to drain modulation of the MOSFET and driver circuit, a negative voltage module is also required to provide gate modulation to ensure the power amplifier can pinch off. If drain modulation starts before gate modulation, a large current will be generated in the power amplifier, causing it to burn out.

[0058] Figure 1 It is a structural diagram of negative control positive mode; refer to Figure 1 , VDD represents the positive power supply of the drain power modulation module, referred to as the drain power supply. VEE represents the negative power supply. In related technologies, a fixed-delay negative-to-positive control method integrates a drain driver, a negative-to-empty positive delay module, and a transistor Q1 in the drain power modulation circuit. Transistor Q1 can be a power MOSFET. The output of the negative-to-empty positive delay module is connected to the enable terminal of the drain power modulation circuit. After the negative power supply is turned on, the drain power modulation is turned on within a fixed time to implement power-on sequence protection for the power devices.

[0059] Traditional negative-controlled positive modules integrated into drain modulation have the following disadvantages: First, this solution relies on a fixed high delay time and has poor applicability; second, when the power amplifier is operating normally, if the negative voltage bias output is abnormal (for example, it drops to close to 0V), this solution cannot provide real-time feedback of the abnormality, which will cause the power amplifier current to surge and damage the power amplifier or drain modulation devices.

[0060] An embodiment of the present invention provides a negative-controlled positive-negative voltage bias circuit, which integrates a negative-controlled positive function with a negative voltage bias and simultaneously samples the negative power supply voltage and the negative voltage bias output voltage to solve the problems of poor applicability and poor safety of the existing fixed-delay negative-controlled positive method.

[0061] Figure 2 Schematic diagram of the application scenario of the negative control positive and negative voltage bias circuit provided by the embodiment of the present invention; Figure 2 Exemplarily, the negative-controlled positive-negative voltage bias circuit inputs a negative power supply, outputs a negative voltage bias to the gate of the power amplifier, and outputs an enable signal to control the drain modulation module.

[0062] It should be noted that the negative control positive and negative voltage bias circuit can determine the input power state of the drain modulation module based on the state of the drain power supply. Exemplarily, the negative control positive and negative voltage bias circuit can also input the drain power supply, output an enable signal based on the negative power supply and the drain power supply, and control the drain modulation module. There is no limitation on how the negative control positive and negative voltage bias circuit is connected to the drain power supply. Exemplarily, when the drain power supply is a low voltage power supply, such as 5V or 12V, the drain power supply can be directly connected to the negative control positive and negative voltage bias circuit. In another exemplary embodiment, when the drain power supply is a high voltage power supply, the negative control positive and negative voltage bias circuit is indirectly connected to the drain power supply through a step-down unit.

[0063] Figure 3 Schematic diagram of the structure of the negative control positive and negative voltage bias circuit provided by the embodiment of the present invention; Figure 3 , the circuit includes: a negative voltage bias module and a negative control positive module.

[0064] Among them, the negative voltage bias module includes a negative voltage bias unit; the input end of the negative voltage bias unit is used to connect to a negative power supply, and the output end is used to output a negative voltage bias to the gate of the power amplifier.

[0065] The negative-to-positive module includes a power-on protection unit, a power-off protection unit, and a trigger unit.

[0066] Here, the power-on protection unit outputs a power-on protection signal when both the negative power supply and the negative voltage bias are powered on; the power-off protection unit outputs a power-off protection signal when at least one of the negative power supply or the negative voltage bias is powered off; the trigger unit outputs a drain modulation module start signal based on the power-on protection signal, or outputs a drain modulation module shutdown signal based on the power-off protection signal, wherein the drain modulation module is used to modulate the drain of the power amplifier.

[0067] In some embodiments, the circuit includes: a negative voltage bias module and a negative control positive module;

[0068] In some embodiments, the negative voltage bias module includes a negative voltage bias unit; the input end of the negative voltage bias unit is used to connect to a negative power supply, and the output end is used to output a negative voltage bias to the gate of the power amplifier.

[0069] Exemplarily, the specific value of the negative voltage bias is related to the power amplifier. Exemplarily, the power amplifier is a depletion-mode power amplifier. Exemplarily, for the power amplifier, when no gate control voltage is applied, the device remains normally on; when a negative gate control voltage is applied, the device's conductivity weakens; and when the gate control voltage exceeds a certain negative threshold, the device is completely turned off.

[0070] In some embodiments, the negative-to-positive module includes a power-on protection unit, a power-off protection unit, and a trigger unit.

[0071] In some embodiments, the power-on protection unit outputs a power-on protection signal when both the negative power supply and the negative voltage bias are powered on.

[0072] Exemplarily, the negative power supply outputs a negative voltage. Further exemplarily, the negative power supply being powered on indicates that the negative power supply outputs a negative voltage whose absolute value is greater than a preset value, or indicates that the negative power supply outputs a negative voltage whose absolute value is less than a preset threshold.

[0073] Exemplarily, the negative voltage bias power-on indicates that the absolute value of the negative voltage of the negative voltage bias is greater than a preset value, or indicates that the negative voltage bias unit outputs a negative voltage less than a preset threshold.

[0074] Exemplarily, the power-on protection signal is output only when both the negative power supply and the negative voltage bias are powered on.

[0075] In some embodiments, the power-off protection unit outputs a power-off protection signal when at least one of the negative power supply or the negative voltage bias is powered off.

[0076] Exemplarily, the negative power supply being powered off means that the absolute value of the voltage output by the negative power supply is not greater than a preset value, such as 0.

[0077] Exemplarily, the negative voltage bias power-off means that the absolute value of the voltage output by the negative voltage bias unit is not greater than a preset value, such as 0.

[0078] Exemplarily, powering off at least one of the negative power supply or the negative voltage bias includes powering off only the negative power supply, powering off only the negative voltage bias, or powering off both the negative power supply and the negative voltage bias. For example, when the negative power supply is normal and the negative voltage bias unit is abnormal, only the negative voltage bias is powered off. For another example, when the negative power supply is abnormal, the negative voltage bias will also become abnormal after a certain period of time, i.e., both the negative power supply and the negative voltage bias are powered off.

[0079] It should be noted that the power-on / power-off thresholds for the negative power supply and the negative bias voltage do not need to be the same. Typically, the negative power supply voltage is greater than the negative bias voltage. Furthermore, in a specific circuit, the specific voltage used to represent the power-on and power-off protection signals is not limited.

[0080] In some embodiments, the trigger unit outputs a drain modulation module start signal based on a power-on protection signal, or outputs a drain modulation module shut-down signal based on a power-off protection signal, wherein the drain modulation module is used to modulate the drain of the power amplifier.

[0081] Exemplarily, the trigger unit outputs an enable signal, which is used to control the on or off of the drain modulation module. It should be noted that in a specific circuit, the specific voltage used to represent the enable signal of the drain modulation module is not limited.

[0082] For example, when the power-on protection unit outputs a power-on protection signal, the trigger unit outputs a drain modulation module start-up signal based on the power-on protection signal.

[0083] For another example, when the power-off protection unit outputs a power-off protection signal, the trigger unit outputs a drain modulation module shut-down signal based on the power-off protection signal.

[0084] Exemplarily, the trigger unit outputs a normally closed signal to control the drain modulation module to shut down. For example, before the power-on protection unit outputs a power-on protection signal, the trigger unit outputs a drain modulation module shutdown signal. For another example, when the power-on protection unit outputs a power-on protection signal and the drain modulation module is turned on, during normal operation of the power amplifier, if the power-off protection unit outputs a power-off protection signal, the trigger unit outputs a drain modulation module shutdown signal based on the power-off protection signal. Before the power-on protection unit outputs a power-on protection signal, the trigger unit outputs a drain modulation module shutdown signal.

[0085] The embodiment of the present invention integrates a negative voltage bias circuit with a negative control positive function, and samples the negative power supply voltage and the negative voltage bias output voltage at the same time. When the negative power supply and the negative voltage bias are both powered on, a power-on protection signal is generated. The trigger unit generates a start signal based on the power-on protection signal, and then controls the drain modulation module to turn on, ensuring that the gate voltage modulation is fully turned on before the drain voltage modulation is turned on, so as to ensure that the power-on sequence of the power amplifier is gate first and then drain, thereby avoiding burning the power amplifier. When either the negative power supply or the negative voltage bias loses power, a power-off protection signal is generated. The trigger unit generates a shutdown signal based on the power-off protection signal, and then controls the drain modulation module to turn off. When an abnormal power-off occurs in the gate voltage modulation, the drain power modulation is turned off to avoid burning the power amplifier, thereby improving the safety of the system. At the same time, the present invention avoids the use of a fixed delay method, is applicable to different power amplifier control timings, and has improved applicability.

[0086] The conventional timing control method is to add a delay to the sampling port of the negative-controlled positive of the drain modulation driver, and turn on the drain modulation within a fixed time after the negative power supply is turned on. However, if the gate modulation is not turned on due to unexpected reasons before it is turned on or an output abnormality occurs after it is turned on, the power amplifier will burn out instantly. The embodiment of the present invention proposes a negative voltage bias circuit structure with an integrated negative control positive function, which can simultaneously sample the negative power supply voltage and the output voltage of the negative voltage bias module to ensure that the drain modulation is turned on after the gate modulation drive works. When abnormal jitter is introduced into the gate of the power amplifier, an abnormal signal can be output, and the drain modulation of the power amplifier can be turned off in time through the negative control positive function. The embodiment of the present invention is based on the negative control positive circuit of the power amplifier gate modulation, which is composed of a negative voltage bias unit and a negative control positive unit. It ensures that the gate voltage modulation is fully turned on before the drain voltage modulation is turned on, and turns off the drain power modulation when an abnormal power failure occurs in the gate voltage modulation, to ensure that the power amplifier is not burned, thereby improving the safety of the system.

[0087] The present invention implements this circuit design using a 0.5µm BCD process. The circuit, constructed using this architecture, was tested and verified after tape-out. Test results demonstrate that the driver, employing the proposed LDO circuit structure with integrated negative-to-positive control, has a negative supply voltage range of -4.5 to -5.5V, a negative bias output voltage range of -0.4V to -3.5V, and a current capability of ±200mA. Its positive supply voltage range is 5 to 12V, meeting the requirements of most power amplifiers.

[0088] In one possible implementation, the negative voltage bias module also includes a reference voltage unit and a negative voltage bias sampling unit; the reference voltage unit outputs a negative power supply reference voltage, a negative voltage bias power-on reference voltage, and a negative voltage bias power-off reference voltage; the negative voltage bias sampling unit outputs a negative voltage bias sampling voltage.

[0089] The negative-to-positive module further includes a negative power sampling unit, which outputs a negative power sampling voltage. Exemplarily, the negative power sampling unit includes a first negative power sampling unit and a second negative power sampling unit.

[0090] The power-on protection unit includes a first power-on unit and a second power-on unit; the reference voltage unit and the first negative power supply sampling unit are connected to the first power-on unit, and the first power-on unit determines that the negative power supply is powered on when the negative power supply sampling voltage is less than the negative power supply reference voltage; the reference voltage unit and the negative voltage bias sampling unit are connected to the second power-on unit, and the second power-on unit determines that the negative voltage bias is powered on when the negative voltage bias sampling voltage is less than the negative voltage bias power-on reference voltage.

[0091] The power-off protection unit includes a first power-off unit and a second power-off unit; the reference voltage unit and the second negative power sampling unit are connected to the first power-off unit, and the first power-off unit determines that the negative power supply is powered off when the negative power supply sampling voltage is greater than or equal to the negative power supply reference voltage; the reference voltage unit and the negative voltage bias sampling unit are connected to the second power-off unit, and the second power-off unit determines that the negative voltage bias is powered off when the negative voltage bias sampling voltage is greater than or equal to the negative voltage bias power-off reference voltage.

[0092] In some embodiments, the reference voltage unit outputs multiple reference voltages. The reference voltages serve as a reference for determining power-on and power-off of a negative power supply or a negative voltage bias. Furthermore, the reference voltages are less than or equal to 0.

[0093] Exemplarily, the negative bias power-on reference voltage is less than or equal to the negative bias power-off reference voltage. For example, the negative bias power-on reference voltage may be -0.9V. For another example, the negative bias power-off reference voltage may be -0.7V. For another example, the negative power supply reference voltage may be -0.1V.

[0094] In some embodiments, the negative voltage bias sampling unit is used to sample the negative voltage bias and output a negative voltage bias sampling voltage. The negative power supply sampling unit is used to sample the negative power supply and output a negative power supply sampling voltage.

[0095] Exemplarily, the first negative power sampling unit and the second negative power sampling unit each output a negative power sampling voltage. The negative power sampling voltages output by the first negative power sampling unit and the second negative power sampling unit may be the same or different. The first negative power sampling unit outputs the negative power sampling voltage to the first power-on unit. The second negative power sampling unit outputs the negative power sampling voltage to the first power-off unit.

[0096] Furthermore, in some embodiments, the power-on protection unit and the power-off protection unit compare the multiple reference voltages with the negative bias sampling voltage and the negative power supply sampling voltage to determine whether to power on or off. The specific power-on and power-off comparison and judgment process is described below.

[0097] Figure 4 This is a schematic diagram of the structure of the negative control positive module provided by the embodiment of the present invention; Figure 4 ,In some embodiments, the power-on protection unit includes a first power-on unit and a second power-on unit;

[0098] Further, exemplarily, the first power-on unit determines that the negative power supply is powered on when the negative power supply sampling voltage is less than the negative power supply reference voltage. Figure 4 The first power-on unit may be a comparator COM1. The negative terminal of the comparator COM1 inputs a negative power reference voltage VREF1, the positive terminal inputs a negative power sampling voltage P1, and the output terminal outputs a negative power-on signal.

[0099] For example, the reference module output voltage VREF1 is compared with the low power supply voltage sampling point, that is, the negative power supply sampling voltage P1. When the negative power supply voltage VEE reaches -4V, the voltage at point P1 reaches the value of the reference module output voltage VREF1. The resistors R31:R32=1:3. When the value of the negative power supply voltage VEE exceeds the typical value of -4V, the comparator COM1 output flips to a low level VEE.

[0100] Further, exemplarily, the second power-on unit determines the negative voltage bias power-on when the negative voltage bias sampling voltage is less than the negative voltage bias power-on reference voltage; exemplarily, referring to Figure 4 The second power-on unit may be a comparator COM2. The negative terminal of the comparator COM2 inputs a negative bias power-on reference voltage VREF2, the positive terminal inputs a negative bias sampling voltage SAMP, and the output terminal outputs a negative bias power-on signal.

[0101] For example, the reference module output voltage VREF2 is compared with the sampling signal SAMP. When the sampling signal SAMP is less than 70% of the set value, the comparator COM2 output flips to the low level VEE;

[0102] In some embodiments, the power-off protection unit includes a first power-off unit and a second power-off unit;

[0103] Further, exemplarily, the first power-off unit determines that the negative power supply is powered off when the negative power supply sampling voltage is greater than or equal to the negative power supply reference voltage; exemplarily, referring to Figure 4 The first power-off unit may be a comparator COM3. The negative terminal of the comparator COM3 inputs the negative power reference voltage VREF1, the positive terminal inputs the negative power sampling voltage P2, and the output terminal outputs a negative power-off signal.

[0104] For example, the reference module output voltage VREF1 is compared with the negative power supply voltage VEE sampling voltage P2. When the negative power supply voltage VEE is greater than or equal to -3.5V, the sampling voltage P2 reaches the value of VREF1, where the resistors R33:R34=1:2.5, and the comparator COM4 output is flipped to a low level VEE, which is then output to a high level GND through the inverter.

[0105] Further, exemplarily, the second power-off unit determines the negative voltage bias power-off when the negative voltage bias sampling voltage is greater than or equal to the negative voltage bias power-off reference voltage. Figure 4 The second power-off unit may be a comparator COM4. The negative terminal of the comparator COM4 inputs the negative bias power-off reference voltage VREF3, the positive terminal inputs the negative bias sampling voltage SAMP, and the output terminal outputs a negative bias power-off signal.

[0106] For example, the reference module output voltage VREF3 is compared with the sampling signal SAMP. When the sampling signal SAMP is greater than the reference output voltage setting value VREF3, the comparator COM4 output is flipped to a low level VEE, and outputs a high level GND through the inverter.

[0107] The power-off protection unit of the embodiment of the present invention can prevent the ripple in the negative power supply voltage VEE from affecting the output voltage of the negative voltage bias, or can prevent the abnormality in the negative voltage bias, thereby avoiding affecting the output working state.

[0108] Reference Figure 4 In one possible implementation, the first negative power sampling unit includes a resistor R31 and a resistor R32; the input end of the resistor R31 is connected to the negative power supply, and the output end is connected to the resistor R32; the end of the resistor R32 away from the resistor R31 is grounded; and the common terminal of the resistor R31 and the resistor R32 serves as the output end of the negative power sampling voltage.

[0109] In one possible implementation, the second negative power sampling unit includes a resistor R33 and a resistor R34; the input end of the resistor R33 is connected to the negative power supply, and the output end is connected to the resistor R34; the end of the resistor R34 away from the resistor R33 is grounded; and the common end of the resistor R33 and the resistor R34 serves as the output end of the negative power sampling voltage.

[0110] For example, refer to Figure 4 The first negative power sampling unit outputs a negative power sampling voltage P1 to the power-on protection unit. The second negative power sampling unit outputs a negative power sampling voltage P2 to the power-off protection unit. Exemplarily, the first negative power sampling unit and the second negative power sampling unit have the same structure, but different resistance ratios of R31:R32 and R33:R34.

[0111] After determining whether power is on or off, the power-on protection unit and the power-off protection module further output a power-on protection signal and a power-off protection signal.

[0112] In a possible implementation, the power-on protection unit further includes a power-on signal determination unit;

[0113] The power-on signal judgment unit includes a first NOR gate and a first inverter; the first input end of the first NOR gate is connected to the output end of the first power-on unit, the second input end is connected to the output end of the second power-on unit, and the output end is connected to the input end of the first inverter; the output end of the first inverter outputs a power-on protection signal;

[0114] The power-off protection unit also includes a power-off signal judgment unit;

[0115] The power-off signal judgment unit includes a second inverter, a third inverter and a second NOR gate; the input end of the second inverter is connected to the output end of the first power-off unit, and the output end is connected to the first input end of the second NOR gate; the input end of the third inverter is connected to the output end of the second power-off unit, and the output end is connected to the second input end of the second NOR gate; the output end of the second NOR gate outputs the power-off protection signal.

[0116] Reference Figure 4 In some embodiments, the power-on signal determination unit may include a first NOR gate NOR1 and a first inverter INV1. Exemplarily, the NOR gate is also called a NOR logic gate circuit.

[0117] Reference Figure 4 In some embodiments, the power-off signal determination unit may include a second inverter INV2, a third inverter INV3, and a second NOR gate NOR2.

[0118] The specific structures of the negative voltage bias unit, the reference voltage unit and the negative voltage bias sampling unit in the negative voltage bias module are described below.

[0119] Figure 5 is a schematic diagram of the structure of the negative pressure bias module provided by an embodiment of the present invention; Figure 5 In one possible implementation, the negative voltage bias unit includes an operational amplifier OP1, an adjustment tube, a resistor RADJ, and a resistor R1; the negative terminal of the operational amplifier OP1 inputs a reference voltage, and the output terminal is connected to the gate of the adjustment tube; the drain of the adjustment tube is connected to a negative power supply, and the source is connected to the resistor RADJ; the source serves as an output terminal for outputting a negative voltage bias to the gate of the power amplifier;

[0120] The resistor RADJ is connected in series with the resistor R1; the end of the resistor R1 away from the resistor RADJ is grounded;

[0121] A common terminal of the resistor RADJ and the resistor R1 is connected to the positive terminal of the operational amplifier OP1 and is also connected to the input terminal of the negative voltage bias sampling unit.

[0122] Reference Figure 5 , exemplarily, the negative voltage bias unit is a low voltage stabilizing structure, which outputs a negative voltage bias VNLDO to the gate of the power amplifier.

[0123] Exemplarily, the adjustment transistor may be an NMOS adjustment transistor.

[0124] Exemplarily, a common terminal ADJ of the resistor RADJ and the resistor R1 is a sampling port connected to an input terminal of the negative voltage bias sampling unit.

[0125] Exemplarily, a reference voltage is input to the negative terminal of the operational amplifier OP1 , and the reference voltage may be provided by a reference voltage unit.

[0126] Figure 6 is a schematic diagram of the structure of the reference voltage unit provided by an embodiment of the present invention; Figure 6 In one possible implementation, the reference voltage unit includes a bandgap reference voltage source, an operational amplifier OP2, a transistor MP1, and a resistor divider unit; the bandgap reference voltage source is connected to the positive terminal of the operational amplifier OP2; the output terminal of the operational amplifier OP2 is connected to the gate of the transistor MP1; the source of the transistor MP1 is connected to a negative power supply, the drain is connected to the negative terminal of the operational amplifier OP2, and the drain is also connected to the input terminal of the resistor divider unit; the first port of the resistor divider unit outputs a negative power supply reference voltage, the second port outputs a negative voltage bias power-on reference voltage, and the third port outputs a negative voltage bias power-off reference voltage.

[0127] Exemplarily, the transistor MP1 is a PMOS.

[0128] For example, the bandgap reference voltage source generates a voltage of -1.2 V. Due to the presence of the low-voltage power generation unit, the power supply voltage of the reference unit is fixed, and the requirements for the reference structure are relatively low. Therefore, the bandgap reference voltage source can adopt a typical reference structure and output a reference voltage of -1.2 V.

[0129] The reference unit circuit provides a stable reference voltage for the main negative feedback loop, which is beneficial to reducing the impact of power supply voltage and temperature changes on output voltage changes and reducing the amount of output voltage change.

[0130] Exemplarily, the reference voltage unit is a BUFFER structure.

[0131] Exemplarily, the resistor divider unit comprises a plurality of resistors connected in series, for example, five resistors. The common terminal between two resistors is an output terminal of a reference voltage. For example, the common terminal between the first resistor and the second resistor is a first port, which outputs a negative power supply reference voltage VREF1. The common terminal between the second resistor and the third resistor is a second port, which outputs a negative voltage bias power-on reference voltage VREF2. The common terminal between the third resistor and the fourth resistor is a third port, which outputs a negative voltage bias power-off reference voltage VREF3. For another example, the common terminal between the fourth resistor and the fifth resistor is a fourth port, which outputs a reference voltage VREF to the negative terminal of the operational amplifier OP1 of the negative voltage bias unit.

[0132] Exemplarily, the negative power supply reference voltage VREF1 may be -0.1V; the negative bias power-on reference voltage VREF2 may be -0.9V; the negative bias power-off reference voltage VREF3 may be -0.7V; and the reference voltage VREF of the negative bias unit may be -0.4V.

[0133] Figure 7is a schematic diagram of the structure of the negative pressure bias sampling unit provided by an embodiment of the present invention; Figure 7 In one possible implementation, the negative voltage bias sampling unit includes an operational amplifier OP3, a transistor MP2, a resistor R21, and a resistor R22; the positive terminal of the operational amplifier OP3 is connected to the output terminal of the negative voltage bias unit, and the output terminal is connected to the gate of the transistor MP2; the source of the transistor MP2 is connected to a negative power supply, and the drain is connected to the input terminal of the resistor R21, wherein the resistor R21 and the resistor R22 are connected in series, and the end of the resistor R22 away from R21 is grounded; the common terminal of the resistor R21 and the resistor R22 is connected to the negative terminal of the operational amplifier OP3; the common terminal of the drain of the transistor MP2 and the resistor R21 serves as the output terminal of the negative voltage bias sampling voltage.

[0134] Exemplarily, the transistor MP2 is a PMOS.

[0135] Exemplarily, the resistor R21 and the resistor R22 are feedback resistors.

[0136] Exemplarily, the negative voltage bias sampling unit has a buffer structure, which inputs the output voltage of the negative voltage bias unit and outputs a negative voltage bias sampling voltage SAMP. Exemplarily, the negative input terminal and output terminal of the operational amplifier OP3 are short-circuited to form a unity-gain negative feedback loop, which samples the output voltage of the negative voltage bias unit and outputs a sampling signal SAMP. Exemplarily, during normal operation, the voltage value of SAMP is set to -1.0V.

[0137] Exemplarily, the BUFFER structure is a three-stage amplifier structure, which operates using the negative feedback principle.

[0138] Exemplarily, the operational amplifier OP2 has the same structure as the operational amplifier OP3.

[0139] Exemplarily, the positive terminal of the operational amplifier OP3 is connected to the output terminal of the negative voltage bias unit, for example, to the common terminal of the resistor RADJ and the resistor R1 , that is, the sampling port ADJ.

[0140] In one possible implementation, the trigger unit includes an RS trigger and a level transfer unit: the R end of the RS trigger is connected to the output end of the power-on protection unit, the S end is connected to the output end of the power-off protection unit, and the output end is connected to the level transfer unit; the level transfer unit converts the negative level signal output by the RS trigger into a positive level signal, wherein a high level in the positive level signal indicates a drain modulation module on signal, and a low level indicates a drain modulation module off signal.

[0141] The working mode is as follows:

[0142] During the power-on process, when the values of the negative power supply voltage VEE and the negative voltage bias unit output port VNLDO both reach the set threshold, the power-on protection signal a will output a high level GND. After passing through the inverter and RS trigger, the output signal OUT is set to a high level GND.

[0143] During the power-off process, when the value of the negative power supply voltage VEE or the negative voltage bias unit output port VNLDO is greater than the set threshold, the power-off protection signal b will output a low level VEE. After passing through the RS trigger, the output signal OUT is set to a low level VEE.

[0144] The following table shows an exemplary truth table for an RS flip-flop. Signal a represents the power-on protection signal, and signal b represents the power-off protection signal. 0 represents a low-level VEE, and 1 represents a high-level GND. When signal a outputs a high-level GND and signal b outputs a low-level VEE, the switch module functions in an indeterminate state. If signal a outputs a high-level GND, the negative power supply voltage VEE is powered on, and the SAMP signal is normal, signal b outputs a high-level GND, and the indeterminate state does not occur.

[0145]

[0146]

[0147] Exemplarily, the level shift unit realizes the function of inputting 0 to -5V and outputting 0 to 5V.

[0148] Figure 8 Schematic diagram of the structure of the level transfer unit provided by the embodiment of the present invention; Figure 8 In a possible implementation, the level shift unit is further connected to a negative power supply and a drain power supply of the drain modulation module; when the drain power supply is not fully powered on, the level shift unit outputs a drain modulation module shutdown signal.

[0149] Reference Figure 8 The input terminal IN is connected to the output terminal of the RS trigger, and the output terminal OUT is connected to the enable terminal of the drain modulation module. The VEE terminal is connected to the negative power supply. The VDD terminal is connected to the power supply of the drain modulation module.

[0150] Exemplarily, the level shift unit includes an inverter INV21, an inverter INV22, an inverter INV23, a transistor MN1, a transistor MN2, a transistor MN3, a transistor MN4, a transistor MN5, a transistor MN6, a transistor MP21, a transistor MP22, a transistor MP3, a transistor MP4, a transistor MP5, a transistor MP6, a transistor MP7, and a resistor R11. The connection relationship between the various components is shown in FIG. Figure 8 connection method.

[0151] Exemplarily, the transistors MN1 to MN4 are NMOS transistors.

[0152] Exemplarily, the transistor MP21 , the transistor MP22 , the transistor MP3 , the transistor MP4 , the transistor MP5 , the transistor MP6 , the transistor MP7 , the transistor MN5 , and the transistor MN6 are high-voltage power transistors.

[0153] For example, the input signal IN passes through inverter INV21 to generate a signal inverse to the input signal IN. This signal is then connected to the gate of MN2 and the input of inverter INV22. The output of inverter INV22 generates a signal in phase with the input signal IN and is connected to the gate of MN1. MN1, MN3, MP21, MP22, MN5, MN6, MN2, MN4, MP3, MP4, and their interconnections form the core of the level shifting module, enabling the generation of a 0-5V digital output signal from a 0-5V input. MP5, MP6, MP7, R11, and their interconnections form the set circuit for the OUT signal. When the VEE level is 0V, the voltages at ports 1 and 2 are high, and the output voltage is 0V, preventing the OUT signal from being high due to powering on after the negative power supply voltage VEE. Inverter INV23 acts as a shaper, shaping the input signal and outputting the OUT signal. Specific circuit values and specifications are shown in the table below. By default, the negative power supply is established.

[0154] Drain supply voltage IN OUT 0V VEE 0V 0V 0V 0V VDD VEE 0V VDD 0V VDD

[0155] For example, if VDD power-up is not complete, a low-level signal is output. After VDD power-up is complete, the chip's OUT port will output a high-level signal only when both the VEE port and the VNLDO port voltages meet the set values. After power-up is complete, if either the VEE port or the VNLDO port experiences an abnormality and falls below the set value, the chip's OUT port will output a low-level signal.

[0156] The present invention provides a power amplifier protection circuit, comprising a negative-controlled positive and negative voltage bias circuit as in any one of the possible implementations described above.

[0157] For example, a negative voltage bias with an integrated negative-to-positive function can provide stable and controllable peripheral modulation for a power amplifier.

[0158] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A negative-controlled positive and negative voltage bias circuit, characterized in that: Including negative voltage bias module and negative control positive module; The negative voltage bias module includes a negative voltage bias unit; the input end of the negative voltage bias unit is used to connect to a negative power supply, and the output end is used to output a negative voltage bias to the gate of the power amplifier; the negative voltage bias module also includes a reference voltage unit and a negative voltage bias sampling unit; The reference voltage unit outputs a negative power supply reference voltage, a negative voltage bias power-on reference voltage, and a negative voltage bias power-off reference voltage; the negative voltage bias sampling unit outputs a negative voltage bias sampling voltage; The negative control positive module includes a power-on protection unit, a power-off protection unit and a trigger unit; the negative control positive module also includes a negative power sampling unit; the negative power sampling unit outputs a negative power sampling voltage; the negative power sampling unit includes a first negative power sampling unit and a second negative power sampling unit; The power-on protection unit outputs a power-on protection signal when both the negative power supply and the negative voltage bias are powered on; the power-on protection unit includes a first power-on unit and a second power-on unit; the reference voltage unit and the first negative power supply sampling unit are connected to the first power-on unit, and the first power-on unit determines that the negative power supply is powered on when the negative power supply sampling voltage is less than the negative power supply reference voltage; the reference voltage unit and the negative voltage bias sampling unit are connected to the second power-on unit, and the second power-on unit determines that the negative voltage bias is powered on when the negative voltage bias sampling voltage is less than the negative voltage bias power-on reference voltage; The power-off protection unit outputs a power-off protection signal when at least one of the negative power supply or the negative voltage bias is powered off; the power-off protection unit includes a first power-off unit and a second power-off unit; the reference voltage unit and the second negative power supply sampling unit are connected to the first power-off unit, and the first power-off unit determines that the negative power supply is powered off when the negative power supply sampling voltage is greater than or equal to the negative power supply reference voltage; The reference voltage unit and the negative voltage bias sampling unit are connected to the second power-off unit, and the second power-off unit determines that the negative voltage bias is powered off when the negative voltage bias sampling voltage is greater than or equal to the negative voltage bias power-off reference voltage; wherein the negative voltage bias power-on reference voltage is less than the negative voltage bias power-off reference voltage; The trigger unit outputs a drain modulation module start signal based on the power-on protection signal, or outputs a drain modulation module shut-down signal based on the power-off protection signal, wherein the drain modulation module is used to modulate the drain of the power amplifier; the trigger unit includes an RS trigger and a level shift unit; The R end of the RS trigger is connected to the output end of the power-on protection unit, the S end is connected to the output end of the power-off protection unit, and the output end is connected to the level transfer unit; the level transfer unit converts the negative level signal output by the RS trigger into a positive level signal, wherein the high level in the positive level signal represents the drain modulation module on signal, and the low level represents the drain modulation module off signal.

2. The negative control positive and negative voltage bias circuit according to claim 1, characterized in that: The power-on protection unit further includes a power-on signal judgment unit; The power-on signal judgment unit includes a first NOR gate and a first inverter; the first input end of the first NOR gate is connected to the output end of the first power-on unit, the second input end is connected to the output end of the second power-on unit, and the output end is connected to the input end of the first inverter; the output end of the first inverter outputs a power-on protection signal; The power-off protection unit further includes a power-off signal judgment unit; The power-off signal judgment unit includes a second inverter, a third inverter and a second NOR gate; the input end of the second inverter is connected to the output end of the first power-off unit, and the output end is connected to the first input end of the second NOR gate; the input end of the third inverter is connected to the output end of the second power-off unit, and the output end is connected to the second input end of the second NOR gate; the output end of the second NOR gate outputs a power-off protection signal.

3. The negative control positive and negative voltage bias circuit according to claim 1, wherein: The level shifting unit is also connected to the negative power supply and the drain power supply of the drain modulation module; The level shifting unit outputs a drain modulation module shut-down signal when the drain power supply is not fully powered on.

4. The negative control positive and negative voltage bias circuit according to claim 1, wherein: The negative voltage bias unit includes an operational amplifier OP1, an adjustment tube, a resistor RADJ and a resistor R1; The negative terminal of the operational amplifier OP1 is input with a reference voltage, and the output terminal is connected to the gate of the adjustment tube; The drain of the adjustment tube is connected to a negative power supply, and the source is connected to a resistor RADJ; the source serves as an output end for outputting a negative voltage bias to the gate of the power amplifier; The resistor RADJ is connected in series with the resistor R1; one end of the resistor R1 away from the resistor RADJ is grounded; A common terminal of the resistor RADJ and the resistor R1 is connected to the positive terminal of the operational amplifier OP1 and is also connected to the input terminal of the negative voltage bias sampling unit.

5. The negative control positive and negative voltage bias circuit according to claim 1, wherein: The reference voltage unit includes a bandgap reference voltage source, an operational amplifier OP2, a transistor MP1 and a resistor voltage divider unit; The bandgap reference voltage source is connected to the positive terminal of the operational amplifier OP2; the output terminal of the operational amplifier OP2 is connected to the gate of the transistor MP1; The source of the transistor MP1 is connected to a negative power supply, the drain is connected to the negative terminal of the operational amplifier OP2, and the drain is also connected to the input terminal of the resistor voltage divider unit; The first port of the resistor voltage divider unit outputs a negative power supply reference voltage, the second port outputs a negative voltage bias power-on reference voltage, and the third port outputs a negative voltage bias power-off reference voltage.

6. The negative control positive and negative voltage bias circuit according to claim 1, wherein: The negative voltage bias sampling unit includes an operational amplifier OP3, a transistor MP2, a resistor R21 and a resistor R22; The positive terminal of the operational amplifier OP3 is connected to the output terminal of the negative voltage bias unit, and the output terminal is connected to the gate of the transistor MP2; The source of the transistor MP2 is connected to the negative power supply, and the drain is connected to the input end of the resistor R21, wherein the resistor R21 and the resistor R22 are connected in series, and the end of the resistor R22 away from the resistor R21 is grounded; The common terminal of the resistor R21 and the resistor R22 is connected to the negative terminal of the operational amplifier OP3; the common terminal of the drain of the transistor MP2 and the resistor R21 serves as the output terminal of the negative voltage bias sampling unit.

7. The negative control positive and negative voltage bias circuit according to claim 1, wherein: The first negative power sampling unit includes a resistor R31 and a resistor R32; The input end of the resistor R31 is connected to the negative power supply, and the output end is connected to the resistor R32; One end of the resistor R32 away from the resistor R31 is grounded; A common terminal of the resistor R31 and the resistor R32 serves as an output terminal of the first negative power sampling unit; The second negative power sampling unit includes a resistor R33 and a resistor R34; the input end of the resistor R33 is connected to the negative power supply, and the output end is connected to the resistor R34; the end of the resistor R34 away from the resistor R33 is grounded; the common end of the resistor R33 and the resistor R34 serves as the output end of the negative power sampling unit; wherein, the first negative power sampling unit and the second negative power sampling unit have the same structure, and the resistance ratios of R31:R32 and R33:R34 are different.

8. A power amplifier protection circuit, characterized in that: The negative-controlled positive and negative voltage bias circuit comprises the negative-controlled positive and negative voltage bias circuit according to any one of claims 1 to 7.

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