WO2011026293A1

WO2011026293A1 - Temperature compensating circuit for power amplifier

Info

Publication number: WO2011026293A1
Application number: PCT/CN2009/075982
Authority: WO
Inventors: 余正明
Original assignee: 惠州市正源微电子有限公司
Priority date: 2009-09-04
Filing date: 2009-12-24
Publication date: 2011-03-10
Also published as: CN101656511A

Abstract

A temperature compensating circuit for a power amplifier includes a feedback circuit (2) and a control circuit (1). A control signal (V_tf/I_tf) varied with the variation of the temperature of the power amplifier is generated by the control circuit (1) to adjust the feedback of the feedback circuit (2). The feedback circuit (2) is connected between an input terminal (RFin) and an output terminal (RFout) of the power amplifier. The temperature compensating circuit can reduce the deviation of the gain of the power amplifier when the temperature of the power amplifier is changed, and keep the performance of the power amplifier.

Description

Title of Invention: Power amplifier temperature compensation circuit

[1] Technical field

[2] The present invention relates to the technical field of power amplifiers, and in particular to a power amplifier temperature compensation circuit having a stable gain effect.

[3] Background Art

[4] Power amplifiers are key components in various wireless communication system transmitters. Each communication standard has strict requirements for its various indicators. As the amount of data transmission increases, the current 3G standard puts more emphasis on power amplifiers. For the demanding requirements, on the basis of high linearity and high efficiency, the power amplifier is also required to have good temperature characteristics over the entire temperature range.

GaAs HBT is a high-linearity and high-efficiency RF device that is widely used in linear power amplifier designs in mobile communication systems, but is currently designed with GaAs HBT devices. The performance of the power amplifier has a large deviation at different temperatures, because the temperature change causes the junction voltage drop and the amplification factor of the power transistor to change, which causes the gain of the power amplifier to be greatly affected by the temperature. For a typical secondary power amplifier, the gain varies with temperature by 2 to 3 dB, which causes the performance of the handheld device using the power amplifier to vary greatly with temperature. To compensate for this performance deviation, Temperature compensation techniques are used to compensate for this deviation of the gain of the power amplifier as a function of temperature. In current power amplifier temperature compensation technology, the main focus is on designing a bias circuit with temperature compensation and using a power supply voltage control circuit with temperature compensation to achieve temperature compensation. The bias circuit with temperature compensation focuses on providing a bias current that does not vary with the supply voltage and temperature. It can partially compensate for the voltage drop of the power transistor as a function of temperature, but the amplification factor of the GaAs HBT device is P=qlc/ KT knows that the gain of the amplifier is directly related to the temperature in addition to the bias current Ic. Without affecting the adjustment capability of the bias circuit itself, the method with temperature compensation bias circuit is used to reduce the gain of the power amplifier with temperature. The change is not very effective. For the method of temperature compensation using a temperature-compensated power supply voltage control circuit, since it uses a temperature-dependent power supply voltage to regulate the power amplifier, this temperature compensation method is mainly used to compensate for the loss. The output power varies with temperature, and it does not have much effect on the compensation of the power amplifier gain with temperature. Therefore, current temperature compensation methods have little effect on reducing the gain of the power amplifier as a function of temperature.

[6] Summary of the invention

[7] The problem to be solved by the present invention is to provide a temperature compensation circuit capable of effectively reducing the variation of the power amplifier gain with temperature.

[8] In order to solve the above problems, the basic technical solution adopted by the present invention is: Providing a power amplifier temperature compensation circuit for suppressing a deviation of a power amplifier gain with a temperature change, specifically including a feedback loop and a And a control circuit, the control circuit generates a control signal that varies with a temperature change of the power amplifier chip to adjust a feedback amount of the power amplifier feedback loop, and the feedback loop is connected between the input and the output of the power amplifier. The function relationship of the control voltage (control current Itf) generated by the control circuit is Vtf=VtfO+f(T) (ltf=ItfO+f(T)); where f(T) is the temperature compensation function, VtfO (wo) Take the temperature (current value) of the control circuit output at a normal temperature of 25 °C.

[9] A preferred solution is: the feedback loop contains a diode (which can be replaced by a PN junction in a transistor of a different material), and the amount of feedback of the power amplifier is controlled by controlling the degree of conduction of the diode.

[10] A more preferred solution is: The feedback loop contains a field effect transistor, and the amount of feedback of the power amplifier is controlled by controlling the degree of conduction of the field effect transistor.

[11] Compared with the prior art, the beneficial effects of the present invention are:

[12] 1) By adjusting the feedback amount of the power amplifier to compensate the change of the power amplifier gain with temperature, this can reduce the change of gain with temperature without affecting other indicators such as the efficiency of the power amplifier;

[13] 2) Using the temperature compensation circuit, when the temperature changes within the range of -20~80 °C, the gain variation of the power amplifier is less than ±0.5 dB;

[14] 3) The circuit structure of the present invention is simple, and the improvement of the compensation performance of the power amplifier gain with temperature does not increase the cost.

[15] BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic block diagram of an embodiment of a temperature compensation circuit according to the present invention; FIG. 2 is a circuit schematic diagram of a first preferred embodiment of the temperature compensation circuit according to the present invention; Circuit diagram of a preferred embodiment; FIG. 4 is a circuit diagram of a third preferred embodiment of the temperature compensation circuit of the present invention FIG. 5 is a comparison diagram of gain versus temperature of a secondary power amplifier using the temperature compensation circuit and the temperature compensation circuit of the present invention.

[17] Specific implementation

[18] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the following drawings are merely illustrative of the present invention and are not to be construed as limiting the scope of the invention. .

1 is a schematic block diagram of an embodiment of a temperature compensation circuit according to the present invention. As shown, the power amplifier is connected between the input signal and the output signal, the control circuit is connected to the feedback loop, and the feedback loop is connected between the input and output of the power amplifier. The implementation of this embodiment is to use a control circuit to generate a control signal following the temperature change of the chip. The control voltage Vtf (control current Itf) is a function of temperature as Vtf=Vtf 0+f(T) (ltf=ItfO+f (T)) , where f(T) is the temperature compensation function, and then this control voltage (control current) is used to control the feedback amount of the power amplifier feedback loop, by GaAs

The amplification factor of the HBT device = /1^1, the gain of the power amplifier decreases with the rise of the temperature T assuming that the bias current Ic does not change with temperature, and the present invention adjusts the feedback loop of the power amplifier by the control signal. The amount of feedback can effectively compensate for the change in gain with temperature, thus providing temperature compensation.

[20] Referring to Fig. 5, a comparison diagram of the gain of the secondary power amplifier with temperature variation of the patented temperature compensation circuit and the temperature compensation circuit is used. The vertical axis represents the gain, the horizontal axis represents the temperature, the solid line is the gain curve without temperature compensation, and the dotted line is the gain curve with temperature compensation. As can be seen from the figure, after the temperature compensation technique is used, the gain of the power amplifier changes by ±1.2 dB after the temperature changes from -20 ° C to 80 ° C. After the temperature compensation circuit is used, the power amplifier The gain variation is reduced to ±0.5dB.

2 is a circuit schematic diagram of a first preferred embodiment of the temperature compensation circuit of the present invention. The reference voltage generating circuit, the voltage adjusting circuit and the control signal generating circuit are connected in series to form a control circuit, wherein the reference voltage generating circuit is configured to generate a reference voltage VBG that does not vary with temperature and power supply voltage, and a current IPTAT that follows the temperature change. The voltage adjustment circuit converts the temperature-changing current IPTAT into a temperature-varying voltage VPTAT, and simultaneously converts the VBG into a more powerful reference voltage VREF, and the control signal generating circuit combines the voltages VREF and VPTAT to generate a follower chip. temperature change The control signal Vtf or Itf; the resistor R1, the diode D1 and the capacitor CI are serially connected between the output end and the input end of the amplifier, and the cathode of the diode D1 is connected to the control circuit through the resistor R2, the resistor R1, the resistor R2, the diode D1 Together with capacitor C1, a feedback loop is formed in which the diode can be replaced by a PN junction of transistors of various materials; transistor Q1 is used for power amplification, and inductor L1 is a choke inductor. When the temperature changes, the control circuit generates a control signal Vtf or Itf that follows the temperature change. The control signal further controls the conduction level of the diode D1 connected to the output of the control circuit, thereby changing the feedback of the feedback loop of the power amplifier at different temperatures. Amount to compensate for the gain of the power amplifier as a function of temperature.

3 is a circuit schematic diagram of a second preferred embodiment of the temperature compensation circuit of the present invention. The base of the transistor Q1 is connected to the input signal, the collector is connected to the inductor L1 and the output signal, and the emitter is grounded; the other end of the inductor L1 is connected to the power source _VCC ; the capacitor _C l , the resistor R1 and the capacitor C2 are serially connected to the transistor Q1 Between the base and the collector, the anode of the diode D1 is first connected to the junction of the resistor R1 and the capacitor C2, and then connected to the output terminal of the control circuit through the resistor R2, and the cathode is grounded. Transistor Q1 is used for power amplification, and inductor L1 is a choke inductor; capacitor Cl, resistor R1, resistor R2, capacitor C2, and diode D1 form a feedback loop. When the temperature changes, the control circuit generates a control signal Vtf or Itf following the temperature change, and the control signal further controls the conduction degree of the diode D1 at different temperatures, thereby changing the feedback amount of the power amplifier feedback loop at different temperatures, It compensates for the gain of the power amplifier as a function of temperature.

4 is a circuit schematic diagram of a third preferred embodiment of the temperature compensation circuit of the present invention. The base of the transistor Q1 is connected to the input signal, the collector is connected to the inductor L1 and the output signal, and the emitter is grounded; the other end of the inductor L1 is connected to the power source _VCC ; the capacitor _C l , the resistor R1 and the capacitor C2 are serially connected to the transistor Q1 Between the base and the collector, the drain of the field effect transistor M1 is connected to the junction of the resistor R1 and the capacitor C2, the gate is connected to the output of the control circuit, and the source is grounded. The transistor Q1 is used for power amplification, and the inductor L1 is a choke inductor; the capacitor C1, the resistor R1, the capacitor C2, and the field effect transistor M1 constitute a feedback loop. When the temperature changes, the control circuit generates a control voltage Vtf following the temperature change, and the control voltage further controls the conduction degree of the field effect transistor M1 at different temperatures, thereby changing the feedback amount of the power amplifier feedback loop at different temperatures, It compensates for the gain of the power amplifier as a function of temperature.

[24] The implementation of the control circuit in the foregoing embodiment is not unique, and may be implemented in different manners. These implementation manners can be implemented by those skilled in the art according to the description in the present invention, and are not praised here. The diodes in the various embodiments may be replaced by PN junctions in transistors of different materials; The above temperature compensation method is also applicable to an amplifier made of different materials to suppress the change of the amplifier gain with respect to temperature.

It should be noted that any minor changes and equivalent substitutions made thereto without departing from the inventive concept are intended to be within the scope of the invention.

Claims

Claim

1. A power amplifier temperature compensation circuit for suppressing a deviation of a power amplifier gain with a temperature change, comprising: a feedback loop and a control circuit, wherein the control circuit generates a change according to a temperature change of the power amplifier chip; The control signal is used to adjust the feedback amount of the power amplifier feedback loop, and the feedback loop is connected between the power amplifier input and the output.

2. The power amplifier temperature compensation circuit according to claim 1, wherein

: The control signal generated by the control circuit is a voltage signal Vtf, and its function relationship is Vtf = VtfO + f(T); wherein f(T) is a temperature compensation function, and VtfO takes a temperature of 25 ° C at a normal temperature, and the output of the control circuit Voltage value.

3. The power amplifier temperature compensation circuit according to claim 1, wherein

: The control signal generated by the control circuit is a current signal Itf, and its function relationship is Itf=I tfO+f(T); wherein f(T) is a temperature compensation function, and ItfO takes a temperature of normal temperature 25 ° C 吋 control circuit output Current value.

4. The power amplifier temperature compensation circuit according to claim 1, wherein

: The feedback loop contains a diode that changes the amount of feedback from the power amplifier by controlling the conduction level of the diode.

5. The power amplifier temperature compensation circuit according to claim 1, wherein: the feedback loop includes a field effect transistor, and the feedback amount of the power amplifier is changed by controlling the conduction degree of the field effect transistor.

A power amplifier temperature compensating circuit according to claim 1, wherein: ???said control circuit comprises a reference voltage generating circuit, a voltage adjusting circuit and a control signal generating circuit.

7. The power amplifier temperature compensation circuit according to claim 3, wherein: the diode in the feedback loop is replaced by a PN junction in a transistor of a different material.