CN219124181U

CN219124181U - Bias circuit

Info

Publication number: CN219124181U
Application number: CN202320063505.7U
Authority: CN
Inventors: 邓小东; 张宗楠; 李一虎; 樊龙; 崔博华
Original assignee: IPGoal Microelectronics Sichuan Co Ltd
Current assignee: IPGoal Microelectronics Sichuan Co Ltd
Priority date: 2023-01-10
Filing date: 2023-01-10
Publication date: 2023-06-02
Anticipated expiration: 2033-01-10

Abstract

The utility model discloses a bias circuit which is applied to a radio frequency amplifier and comprises a temperature feedback unit and a signal coupling unit which are electrically connected with each other, wherein the signal coupling unit is also electrically connected with the radio frequency amplifier to adjust the linearity of the radio frequency amplifier, the temperature feedback unit is adjacent to the radio frequency amplifier to sense the temperature change of the radio frequency amplifier, and the temperature compensation is carried out on the radio frequency amplifier in real time according to the temperature change condition. The bias circuit can perform temperature compensation and linear compensation on the radio frequency amplifier, so that the temperature of the radio frequency amplifier is more stable, the linearity of the power tube is better, and the dynamic performance adjustment capability of the radio frequency amplifier circuit is improved.

Description

Bias circuit

Technical Field

The utility model relates to the field of radio frequency microwaves, in particular to a bias circuit.

Background

The conventional power amplifier can achieve linear amplification of the target signal when operating at its optimal quiescent point (i.e., within the transistor linear region), but the equivalent circuit of the power transistor will also change when the temperature of the transistor itself, which is the power transistor, increases. The power transistor now enters the non-linear region, so that the linearity of the amplifier system is reduced. A common solution is to add a bias circuit to improve the linearity of the amplifier system.

As shown in fig. 1, a conventional bias circuit structure is shown, and the bias circuit has the advantage of simple and practical structure. The temperature feedback loop is mainly composed of a transistor HBT3 and a transistor HBT2 to achieve temperature stability. The power transistor HBT0 increases in temperature and its turn-on voltage VBE0 decreases, and the quiescent current IB1 of the transistor HBT1 increases accordingly, resulting in an increase in the bias circuit output current. However, when the temperature increases to increase the quiescent current of the main channel, the turn-on voltage of the transistor HBT3 in the bias network is also reduced, so that the base current of the transistor HBT2 is reduced, the base potential VB1 is reduced, the base voltage of the transistor HBT1 is reduced, and the output current IB1 is correspondingly reduced.

The bias circuit is simple in structure, the bias circuit can be built only by three transistors, a negative feedback network with temperature characteristics is formed, and temperature stability is realized. And the current change caused by the sensitivity of different transistors to temperature can achieve the effect of selecting proper negative feedback by adjusting the resistor R3.

The bias circuit has a simple structure and can realize the function of temperature feedback, but the temperature feedback circuit can have a certain influence on a main path (radio frequency path). Because the temperature feedback circuit is directly connected with the main passage, partial direct current and alternating current signals of the main passage can directly flow into the temperature feedback circuit, and the signals can influence the induction of the temperature feedback circuit to the main passage. Meanwhile, the direct current signals in the temperature feedback circuit can flow into the main path through the resistor R3, and when the temperature feedback circuit starts to work, the linearity of the main path can be directly affected by the changed direct current signals.

As can be seen from the circuit, the emitter current IE of transistor HBT1 is related to the load resistance R3, IE decreasing if R3 increases. In a simple resistive load emitter follower, although signal coupling can be achieved by only two elements, the linearity of the output signal of this structure is greatly affected by the elements themselves and the operating environment of the elements.

The gain of a typical HBT transistor is calculated as:

in this circuit, HBT1 functions to couple the temperature signal, requiring an ideal value of 1 for a. However, under the influence of the simple resistive load R3, the static operating point thereof shifts (from the point L1 to the point L2 in fig. 2), the emission current IE increases and decreases with the up-and-down swing of the output, and the value of a cannot be maintained around 1. This makes it impossible for HBT1 coupled as a signal to effect the transfer of a real signal. The temperature module impedance change caused by the temperature change affects the input main path signal with the temperature increase.

Accordingly, there is a need to provide an improved bias circuit that overcomes the above-described drawbacks.

Disclosure of Invention

The utility model aims to provide a bias circuit which is suitable for a radio frequency amplifier, and can perform temperature compensation and linear compensation on the radio frequency amplifier, so that the temperature of the radio frequency amplifier is more stable, the linearity of a power tube is better, and the dynamic performance adjustment capability of the radio frequency amplifier circuit is improved.

In order to achieve the above-mentioned objective, the present utility model provides a bias circuit, which is applied to a radio frequency amplifier, wherein the bias circuit includes a temperature feedback unit and a signal coupling unit that are electrically connected to each other, the signal coupling unit is also electrically connected to the radio frequency amplifier to adjust the linearity of the radio frequency amplifier, the temperature feedback unit is adjacent to the radio frequency amplifier to sense the temperature change of the radio frequency amplifier, and performs temperature compensation on the radio frequency amplifier in real time according to the temperature change; the signal coupling unit comprises a first transistor, a second transistor, a third transistor, a fourth transistor and a first resistor, wherein the emitter of the first transistor is connected with the collector of the second transistor and is connected with the radio frequency amplifier, the collector of the first transistor is connected with an external first power supply, the base of the first transistor is connected with the emitter of the third transistor, the emitter of the second transistor is connected with an external second power supply, the base of the second transistor is connected with the base of the fourth transistor, the base of the third transistor is connected with the temperature feedback unit, the collector of the third transistor is connected with the collector of the fourth transistor, the emitter of the fourth transistor is connected with an external second power supply, the base of the fourth transistor is commonly connected with the collector of the fourth transistor, one end of the first resistor is connected with an external first power supply, and the other end of the first resistor is connected with the base of the first transistor.

Preferably, the signal coupling unit further includes a capacitor, one end of the capacitor is connected to the base of the third transistor, and the other end of the capacitor is grounded.

Preferably, the third transistor is a PNP transistor.

Preferably, the temperature feedback unit includes a fifth transistor and a sixth transistor, where a gate of the fifth transistor is connected to a gate of the third transistor, a gate and a collector of the fifth transistor are both connected to an external third power supply, an emitter of the fifth transistor is connected to a collector and a gate of the sixth transistor, and an emitter of the sixth transistor is grounded.

Preferably, the temperature feedback unit further comprises a second resistor, one end of the second resistor is connected with an external third power supply, and the other end of the second resistor is commonly connected with the collector electrode and the grid electrode of the fifth transistor.

Compared with the prior art, the bias circuit disclosed by the utility model is used for collecting and transmitting corresponding current signals with temperature feedback effect through the temperature feedback unit to flow into the signal coupling unit, and the output current of the signal coupling unit is coupled into the base electrode of the power tube of the radio frequency amplifier, so that the specific current of the output current of the bias circuit can be regulated through regulating the coupling unit, the required bias current can be obtained, the temperature compensation of the radio frequency amplifier is further realized, and the linearity of the radio frequency amplifier is improved.

The utility model will become more apparent from the following description taken in conjunction with the accompanying drawings which illustrate embodiments of the utility model.

Drawings

Fig. 1 is a circuit diagram of a prior art bias circuit.

Fig. 2 is a graph of static operating point variation for the circuit structure of fig. 1.

Fig. 3 is a schematic circuit diagram of a bias circuit according to the present utility model.

FIG. 4 is a graph comparing the bias current of the bias circuit of the present utility model with the bias current of the prior art.

Detailed Description

Embodiments of the present utility model will now be described with reference to the drawings, wherein like reference numerals represent like elements throughout. As described above, the bias circuit provided by the utility model is suitable for the radio frequency amplifier, and can perform temperature compensation and linear compensation on the radio frequency amplifier, so that the temperature of the radio frequency amplifier is more stable, the linearity of the power tube is better, and the dynamic performance adjustment capability of the radio frequency amplifier circuit is improved.

Referring to fig. 3, as shown in the drawing, the bias circuit of the present utility model is mainly applied to a radio frequency amplifier, and includes a temperature feedback unit and a signal coupling unit electrically connected to each other; the signal coupling unit is further electrically connected with the radio frequency amplifier to adjust linearity of the radio frequency amplifier, and specifically, the signal coupling unit is connected with a power tube HBT0 of the radio frequency amplifier to adjust linearity of the power tube HBT 0. The temperature feedback unit is adjacent to the radio frequency amplifier and used for sensing the temperature change of the radio frequency amplifier and carrying out temperature compensation on the radio frequency amplifier in real time according to the temperature change condition; specifically, in practical application, the temperature feedback unit is adjacent to the power tube HBT0 of the radio frequency amplifier, that is, senses a temperature change of the power tube HBT 0. In the utility model, the bias circuit collects and transmits corresponding current IB3 signals with temperature feedback effect through the temperature feedback unit to flow into the signal coupling unit, and the output current IC2 of the signal coupling unit is coupled into the base electrode of the power tube HBT 0; the specific current of the output current IC2 can be adjusted by adjusting the coupling unit, so that a required bias current is obtained, the bias current acts on the power tube HBT0, and further temperature compensation of the radio frequency amplifier is achieved, and linearity of the radio frequency amplifier is improved.

Specifically, the signal coupling unit includes a first transistor HTB1, a second transistor HBT2, a third transistor HBT3, a fourth transistor HBT4, and a first resistor R1, where an emitter of the first transistor HBT1 is connected to a collector of the second transistor HBT2 and to the radio frequency amplifier, a collector of the first transistor HBT1 is connected to an external first power supply Vcc, a base thereof is connected to an emitter of the third transistor HBT3, an emitter of the second transistor HBT2 is connected to a second bias power supply Vdd, a base of the second transistor HBT2 is connected to a base of the fourth transistor HBT4, a base of the third transistor HBT3 is connected to a collector of the fourth transistor HBT4, an emitter of the fourth transistor HBT4 is connected to an external second power supply Vcc, a base of the fourth transistor HBT4 is connected to a common base thereof, the first resistor HBT1 is connected to the first resistor HBT1, and the second resistor HBT1 is connected to the external resistor HBT1 through the first resistor HBT1, and the current value of the first resistor HBT1 is controlled to be smaller. In addition, as a preferred embodiment of the present utility model, the signal coupling unit further includes a capacitor C1, one end of the capacitor C1 is connected to the base of the third transistor HBT3, and the other end is grounded, where in the present utility model, when the rf amplifier has an rf signal leaked to the bias circuit, the leaked rf signal can directly pass through the capacitor C1 to the ground, so as to reduce the influence of the rf signal on the bias circuit.

In addition, in the present utility model, the temperature feedback unit includes a fifth transistor HBT5 and a sixth transistor HBT6, wherein a gate of the fifth transistor HBT5 is connected to a gate of the third transistor HBT3, a gate and a collector of the fifth transistor HBT5 are both connected to an external third power source Vbb, an emitter of the fifth transistor HBT5 is connected to a collector and a gate of the sixth transistor HBT6, and an emitter of the sixth transistor HBT6 is grounded; wherein the sixth transistor HBT6 is disposed near the power transistor HBT0 adjacent to the rf amplifier, for sensing the temperature change of the power transistor HBT 0; specifically, when the temperature of the power transistor HBT0 increases, the turn-on voltage VBE0 thereof decreases, and the quiescent current IC6 of the sixth transistor HBT6 also increases, thereby causing the output current of the entire bias circuit to increase; at the same time, however, the fifth transistor HBT5 is turned on and the voltage decreases, so that the base current of the fifth transistor HBT5 decreases, causing the base potential VB5 to decrease, the base voltage of the fifth transistor HBT5 decreases, and the output current IB3 correspondingly decreases. In addition, as a preferred embodiment of the present utility model, the temperature feedback unit further includes a second resistor R2, one end of the second resistor R2 is connected to an external third power source Vbb, and the other end of the second resistor R2 is commonly connected to the collector and the gate of the fifth transistor HBT 5; the external third power supply Vbb thus supplies power to the fifth transistor HBT5 through the second resistor R2, and by controlling the magnitude of the resistance value of the second resistor R2, the magnitude of the current input to the fifth transistor HBT5 can be regulated and controlled.

In the present utility model, as the input rf signal of the rf amplifier increases, the temperature of the power tube HBT0 increases, the turn-on voltage VBE0 thereof decreases, the main path output current IC0 increases, and the output signal of the circuit increases. Similarly, the quiescent current IC6 of the sixth transistor HBT6, which is the sensor transistor, increases. But at the same time that the temperature rise causes an increase of the quiescent current of a part of the rf amplifier, the emitter of the fifth transistor HBT5 of the temperature feedback unit is connected to the collector of the sixth transistor HBT6, and the emitter current thereof increases, so that the base current on the fifth transistor HBT5 decreases, causing the base voltage VB5 to decrease, while the base voltage of the fifth transistor HBT5 decreases, and the base output current thereof also decreases, while the current IB3 acts as a temperature feedback signal, and is coupled to the power transistor HBT0 of the rf amplifier through a current mirror (signal coupling unit) module, i.e. the feedback signal is transferred into the rf amplifier, so that the bias current IC2 obtained by the power transistor HBT0 of the rf amplifier decreases accordingly.

The signal coupling unit is formed by the evolution of a traditional current mirror circuit structure, the voltage VBE3 of the emitter of the third transistor HBT3 of the PNP tube in the signal coupling unit is offset by the upward offset of the voltage VBE4 of the emitter follower of the fourth transistor HBT4 of the NPN tube, and the better phase offset can be realized in practical application; meanwhile, the symmetrical current mirror structure using two transistors (the third transistor HBT3 and the fourth transistor HBT 4) can eliminate the emission current IE caused by the change of the emitter connection resistance load Rb of the transistor (the HBT1 in fig. 1) of the conventional bias circuit, which increases and decreases along with the up-and-down swing of the output, so that the current of the bias circuit is more stable. The emitter output of the first transistor HBT1 is directly cascaded to the base electrode of a power tube HBT0 of the radio frequency amplifier, so that the coupling function of a temperature control feedback signal is realized.

Referring to fig. 4 in combination, the temperature compensation and linearization improvement degree of the bias circuit of the present utility model can be verified by ADS. In verifying the circuit performance of the present utility model, the circuit of the present utility model (the structure shown in fig. 3) was set to be completely identical to the setting operating environment in the simulation of both the prior art circuit (the structure shown in fig. 1). Through simulation software, the circuit is simulated under different conditions respectively, and as shown in a result of fig. 4 (a dotted line is a curve in the prior art, a solid line is a curve of the utility model), when the temperature change is large, the advantages of the bias circuit of the utility model become obvious; when the temperature is increased, the static working point of the whole circuit is further changed, the load impedance is further changed, and the bias circuit adopting the dominant design has better stability.

The utility model has been described in connection with the preferred embodiments, but the utility model is not limited to the embodiments disclosed above, but it is intended to cover various modifications, equivalent combinations according to the essence of the utility model.

Claims

1. The bias circuit is applied to a radio frequency amplifier and is characterized by comprising a temperature feedback unit and a signal coupling unit which are electrically connected with each other, wherein the signal coupling unit is also electrically connected with the radio frequency amplifier and is used for adjusting the linearity of the radio frequency amplifier, and the temperature feedback unit is adjacent to the radio frequency amplifier and is used for sensing the temperature change of the radio frequency amplifier and carrying out temperature compensation on the radio frequency amplifier in real time according to the temperature change condition; the signal coupling unit comprises a first transistor, a second transistor, a third transistor, a fourth transistor and a first resistor, wherein the emitter of the first transistor is connected with the collector of the second transistor and is connected with the radio frequency amplifier, the collector of the first transistor is connected with an external first power supply, the base of the first transistor is connected with the emitter of the third transistor, the emitter of the second transistor is connected with an external second power supply, the base of the second transistor is connected with the base of the fourth transistor, the base of the third transistor is connected with the temperature feedback unit, the collector of the third transistor is connected with the collector of the fourth transistor, the emitter of the fourth transistor is connected with an external second power supply, the base of the fourth transistor is commonly connected with the collector of the fourth transistor, one end of the first resistor is connected with an external first power supply, and the other end of the first resistor is connected with the base of the first transistor.

2. The bias circuit of claim 1 wherein said signal coupling unit further comprises a capacitor having one end connected to the base of the third transistor and the other end connected to ground.

3. The bias circuit of claim 1 wherein said third transistor is a PNP transistor.

4. The bias circuit of claim 1, wherein the temperature feedback unit includes a fifth transistor and a sixth transistor, a gate of the fifth transistor is connected to a gate of the third transistor, a gate and a collector of the fifth transistor are both connected to an external third power supply, an emitter of the fifth transistor is connected to a collector and a gate of the sixth transistor, and an emitter of the sixth transistor is grounded.

5. The bias circuit of claim 4, wherein said temperature feedback unit further comprises a second resistor, one end of said second resistor is connected to an external third power supply, and the other end of said second resistor is commonly connected to a collector and a gate of said fifth transistor.