Patent ID: 12255591

DETAILED DESCRIPTION OF EMBODIMENTS

Specific embodiments of the present disclosure are described in detail below with reference to accompanying drawings.

Specific implementation modes/embodiments described herein are specific embodiments of the present disclosure, and are intended to illustrate a concept of the present disclosure, which are both explanatory and exemplary, and should not be construed as limiting implementation modes and a scope of the present disclosure. In addition to the embodiments described herein, those who skilled in the art shall also use other obvious technical solutions based on claims of the present disclosure and contents disclosed in the specification, and these technical solutions include technical solutions that make any obvious replacement and modification to the embodiments described herein, and are all within a protection scope of the present disclosure.

The present disclosure provides a temperature compensation bias circuit100.

Referring toFIGS.3-5,FIG.3is an application circuit diagram illustrating the temperature compensation bias circuit100of the present disclosure. The present disclosure further provides a power amplifier using the temperature compensation bias circuit100. Specifically, the power amplifier further includes the temperature compensation bias circuit100, a fourth capacitor C4, a second inductor L2, and a radio-frequency (RF) amplification transistor T8.

Circuit connection relationships of the power amplifier are as follows.

A first terminal of the fourth capacitor C4serves as an input terminal RFIN of the power amplifier.

A second terminal of the fourth capacitor C4is respectively connected to an output terminal of a bias circuit module and a base of the RF amplification transistor T8.

An emitter of the RF amplification transistor T8is connected to the ground GND.

A collector of the RF amplification transistor is connected to a second terminal of the second inductor, and the collector of the RF amplification transistor T8serves as an output terminal RFOUT of the power amplifier.

A first terminal of the second inductor L2is connected to a supply voltage VCC.

Specifically, the fourth capacitor C4serves as a blocking capacitor, only an RF signal is capable of passing through the fourth capacitor C4, and a direct-current (DC) voltage is prevented from entering the RF amplification transistor T8.

The second inductor L2is a choke coil or a chip inductor. The second inductor L2is configured to prevent the RF signal from entering a power supply, and only a DC current is capable of passing through the second inductor L2. In the embodiment, the second inductor L2is the choke coil.

The temperature compensation bias circuit100includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a second capacitor C2, a third capacitor C3, a fifth capacitor C5, a fifth transistor T5, a sixth transistor T6, and a seventh transistor T7.

Circuit connection relationships of the temperature compensation bias circuit100are as follows.

A first terminal of the third resistor R3is respectively connected to a first terminal of the fourth resistor R4and a voltage reference VRef.

A second terminal of the third resistor R3is respectively connected to a first terminal of the fifth capacitor C5and a base of the fifth transistor T5.

A second terminal of the fifth capacitor C5is connected to ground GND.

A second terminal of the fourth resistor R4is respectively connected to a collector of the fifth transistor T5, a first terminal of the third capacitor C3, a base of the seventh transistor T7, a first terminal of the second capacitor C2, and a collector of the sixth transistor T6.

A second terminal of the third capacitor C3is connected to the ground GND. A second terminal of the second capacitor C2is connected to a first terminal of the fifth resistor R5.

A second terminal of the fifth resistor R5is respectively connected to a base of the sixth transistor T6and a first terminal of the sixth resistor R6.

An emitter of the sixth transistor T6is connected to the ground GND.

An emitter of the fifth transistor T5is respectively connected to an emitter of the seventh transistor T7, a second terminal of the sixth resistor R6, and a first terminal of the seventh resistor R7.

A collector of the seventh transistor T7is connected to a battery voltage VBat.

A second terminal of the seventh resistor R7serves as an output terminal of the temperature compensation bias circuit100.

An operating principle of the temperature compensation bias circuit100is as follows.

The temperature compensation bias circuit100is configured to provide a bias current for the power amplifier. Specifically, the fifth transistor T5and the seventh transistor T7are combined to provide a base bias current of the RF amplification transistor T8, and satisfy a relationship of IB8=IE5+IE7+IB6. The seventh resistor R7serves as a ballast resistor. The third resistor R3is a base current-limiting resistor of the fifth transistor T5and is capable of adjusting a quiescent operating point of the fifth transistor T5. The fourth resistor R4is a collector resistor of the fifth transistor T5, the fourth resistor R4and the sixth transistor T6jointly determine a quiescent operating point of the seventh transistor T7.

When temperatures of transistors being in quiescent operating points rise, a base current of the RF amplification transistor T8increases, a current IEs of the fifth transistor T5also increases with rise of the temperatures, since a relationship of IE5=IC5+IB5is satisfied, the IB5is much less than IC5, the les is approximately equal to the IC5, the IC5may increase along with the rise of the temperatures. A voltage VC5of the collector of the fifth transistor T5satisfies a relationship of VC5=VCC−IC5×R4, that is, when the IC5increases, the VC5decreases, so that a voltage of the base of the seventh transistor T7and IE7are decreased, thereby decreasing a current of IB8, suppressing the IB8from increasing along with the rise of the temperature, a temperature compensation effect of the temperature compensation bias circuit100is achieved.

In the embodiment, the seventh resistor R7is a parameter-adjustable resistor. The temperature compensation effect of the temperature compensation bias circuit is further adjusted through the adjusting a value of the seventh resistor S7. Compared with a bias scheme in the prior art and the temperature compensation effect of the temperature compensation bias circuit of the present disclosure, please refer toFIG.4,FIG.4is a schematic diagram illustrating comparison between relationship curves of quiescent currents and temperatures respectively in an application circuit of the temperature compensation bias circuit in the related art and an application circuit of the temperature compensation bias circuit100of the present disclosure. As shown inFIG.4, W1is a curve illustrating a relationship between a quiescent current and a temperature of the temperature compensation bias circuit in the prior art, and W2is a curve illustrating a relationship between a quiescent current and a temperature of the temperature compensation bias circuit100of the present disclosure. According to the W2, when the temperature gradually changes from 35° C. to 85° C., the quiescent current output by the temperature compensation bias circuit100increases from 0.088 amps to 0.099 amps, the quiescent current is stable and has very small changes. Temperature drift of the RF amplification transistor T8is significantly less than temperature drift of the temperature compensation bias circuit in the prior at the same normal-temperature quiescent operating current. Therefore, the temperature compensation bias circuit achieves bias circuit temperature compensation, meanwhile, an effect of the ballast resistor is independent of temperature compensation, and the ballast resistor is configured to adjust a gain curve of the power amplifier, so as to adjust a bias to optimize the temperature compensation effect of power amplifier and the linearity of the power amplifier. The seventh resistor R7serves as the ballast resistor and is capable of adjusting a base current of the power amplifier under a high-power input, so as to adjust the gain curve of the power amplifier. The seventh resistor R7is capable of adjusting a gain of the RF amplification transistor T8without participating in the above temperature compensation, thereby almost not affecting temperature compensation performance of this solution. When power of an input signal is too high, swing exceeds a quiescent bias point, a conduction angle decreases, thereby resulting in decrease in a gain of the power amplifier under a large signal input and further causing gain compression.

The temperature compensation bias circuit100is connected to the ground GND through the fifth capacitor C5and the third capacitor C3. The fifth capacitor C5and the third capacitor C3serve as linear capacitors and addition of the fifth capacitor C5and the third capacitor C3enables more RF components to leak to the bias, thereby increasing an emitter current of the fifth transistor T5being in a stable radio frequency state and an emitter current of the seventh transistor T7being in the stable radio frequency state, in this way, IB5=IE7+IE5+IB6is increased, the quiescent bias point of the RF amplification transistor T8under the large signal input is improved, and the gain compression is delayed. The fifth capacitor C5and the third capacitor C3serve as filter capacitors, and whether the temperature compensation bias circuit100includes the filter capacitors connecting to the ground directly affects BES of the RF amplification transistor T8. Please refer toFIG.5,FIG.5is a schematic diagram illustrating relationship curves of VBE8voltages and input power of the temperature compensation bias circuit100of the present disclosure. Specifically, W3is a curve illustrating a relationship between a VBE8voltage and input power of the temperature compensation bias circuit100of the present disclosure, and W4is a curve illustrating a relationship between a VBE8voltage and input power of a circuit, removing the fifth capacitor C5and the third capacitor C3, of the temperature compensation bias circuit100of the present disclosure. According toFIG.5, the temperature compensation bias circuit100includes the filter capacitors connected to the ground, which directly affects the quiescent bias point of the RF amplification transistor T8under a condition that the RF amplification transistor T8increases the large signal input, thereby delaying the gain compression. Flatness of the gain curve at the moment that the gain curve increases along with the input power is further adjusted through adjusting a size ratio of the fifth capacitor C5to the third capacitor C3, and a linearity level of the power amplifier is optimized.

In order to further reduce baseband impedance of the temperature compensation bias circuit100and improve a problem of linearity deterioration of an output signal of the power amplifier. The temperature compensation bias circuit100includes the sixth transistor T6and the sixth resistor R6, the sixth resistor R6is configured to isolate. In a case that there is no RF signal input to the power amplifier, a voltage difference between the supply voltage VCC passing through the fourth resistor R4and the sixth transistor T6is converted into a bias voltage of the seventh transistor T7, thereby generating a bias current IB8, and the bias current IB8is output to an input terminal of the RF amplification transistor T8through the seventh resistor R7. In addition, in a case that is are RF signals input into the power amplifier, the seventh resistor R7blocks most of the RF signals, but there is still partial RF signals leaking from the temperature compensation bias circuit100, specifically, an RF signal attenuated by the seventh resistor R7is isolated from a base low-resistance point of the sixth transistor T6through the sixth resistor R6, so that the RF signal attenuated by the seventh resistor R7is transmitted to the seventh transistor7, thereby passing the RF signal attenuated by the seventh resistor R7. If the RF signal is a large signal (that is, a signal with relatively large power), the emitter of the seventh transistor T7has an RF swing, and the RF swing decreases a bias voltage of a base-emitter junction (BE junction) of the seventh transistor T7through a detection effect of the BE junction, so that IE7output by the emitter of the seventh transistor T7is increased, thereby compensating reduction of a base voltage of the RF amplification transistor T8with increase of the power of the input signal, and suppressing AM-AM distortion of the power amplifier under the large signal.

In the embodiment, the second capacitor C2is a parameter-adjustable capacitor, the fifth resistor R5is a parameter-adjustable resistor.

The second capacitor C2and the fifth resistor R5form a phase margin network. If the RF signal is coupled to the base of the sixth transistor T6through the second capacitor C2and the fifth resistor R5, and the RF signal coupled to the sixth transistor T6enables base potential of the sixth transistor T6to decrease along with the increase of the RF signal through a detection effect of a BE junction of the sixth transistor T6, so that emitter potential of the seventh transistor T7also decreases, resulting in obvious AM-AM distortion of the power amplifier under the large signal, and further causing linearity deterioration of the power amplifier. It can be seen therefrom that introductions of the second capacitor C2and the fifth resistor R5all being parameter-adjustable improves stability of the bias circuit.

In the embodiment, the sixth resistor R6is a parameter-adjustable resistor. The sixth resistor R6for isolation and the second capacitor C2for isolation are switchable. That is, the sixth resistor R6is a variable resistor, and the second capacitor C2is a variable capacitor. Through changing values of the sixth resistor R6and the second capacitor C2and selecting different baseband impedance bandwidths and different noise suppression degrees of the temperature compensation bias circuit100according to different modulation bandwidth signals, thereby increasing applicability and flexibility of a circuit of the temperature compensation bias circuit100.

It should be noted that related circuits, resistors, and transistors used in the present disclosure are all common circuits and components in the art, and corresponding specific indexes and parameters are adjusted according to actual applications, which are not described in detail herein.

Compared with the related art, the temperature compensation bias circuit of the present disclosure includes the fifth transistor, the seventh transistor, and the fourth resistor, when the temperature rises, the current les of the fifth transistor T5also increases with the rise of the temperature, since the relationship of IE5=IC5+IB5is satisfied, the IB5is much less than IC5, the les is approximately equal to the IC5, the IC5may increase along with the rise of the temperature. The voltage VC5of the collector of the fifth transistor T5satisfies the relationship of VC5=VCC−IC5×R4, that is, when the IC5increases, the VC5decreases, so that the voltage of the base of the seventh transistor T7and the IE7are decreased, thereby decreasing the current of IB8, suppressing the IB5from increasing along with the rise of the temperature, the temperature compensation effect of the temperature compensation bias circuit is achieved. As an improvement, the temperature compensation bias circuit of the present disclosure further includes the seventh resistor R7, the temperature compensation effect of the temperature compensation bias circuit is further adjusted through the adjusting the value of the seventh resistor S7. In this way, there are fewer effects on the bias point of the temperature compensation bias circuit when the—compensation bias circuit and the power amplifier are in RF operating states, the power amplifier is enabled to have good temperature compensation effect and high linearity.

It should be noted that the embodiments described above with reference to the accompanying drawings are only used to illustrate a scope of the present disclosure and not to limit the scope of the present disclosure, and those who skilled in the art should understand that modifications or equivalent replacements made to the present disclosure without departing from a spirit and the scope of the present disclosure shall fall within the scope of the present disclosure. Furthermore, unless otherwise noted in the context, words appearing in the singular include plural forms and vice versa. Additionally, all or a portion of any embodiment may be used in connection with all or a portion of any other embodiment unless specifically stated.