Adaptive bias circuit with low loss and temperature compensation, and wireless transmitting system

Abstract

The invention discloses an adaptive bias circuit with low loss and temperature compensation. The adaptive bias circuit comprises a first NPN type triode having a current mirror structure, a second NPN type triode, a transistor, a bias capacitor and a first resistor. By means of a specific circuit connecting structure, the potential of the bias capacitor can be kept unchanged when the input power is increased and does not exceed the critical value, therefore the current of the collector of a power tube is increased with the increase of the input power, and when the input power is further increased and exceeds the critical value, the potential of the bias capacitor is reduced, therefore the current of the collector of the power tube is reduced with the increase of the input power and finally trends to be stable. In addition, the temperature of the power tube can be compensated by the first resistor to improve the thermal temperature. The invention further discloses a wireless transmitting system comprising the above circuit, and the beneficial effects are as mentioned above.

Description

technical field [0001] The invention relates to the technical field of power amplifiers, in particular to an adaptive bias circuit with low loss and temperature compensation and a wireless transmission system. Background technique [0002] The power amplifier plays an important role in wireless communication systems not only because it determines the performance of the system, but also because it is the most energy-consuming component, generating a lot of noise and heat. High-efficiency power amplifiers are designed to improve battery life in wireless end devices with limited battery capacity. A high-efficiency power amplifier requires the power tube to have a low turn-on voltage, a high breakdown voltage and work in a state close to saturation. The bias point and load line of a traditional power amplifier are optimally designed according to the 1dB compression point (P1dB), so that the efficiency of the power amplifier is optimal at the maximum output power. But in actual...

AI Technical Summary

Problems solved by technology

Obviously, in the above method, the bias circuit can improve the linearity of the power amplifier, however, when Q20 is turned on, the current I of the collector of Q20 C,Q20 supplied directly to the base of Q1, to maintain V P Stabilized at the DC potential, when the input signal increases, the current I of the collector of Q20 C,Q20 It will also increase sharply, which will cause the power tube Q1 to have a very large current consumption, resulting in a decrease in the efficiency of the power amplifier

in addition, figure 1 In the bias circuit shown, the power tube Q1 has a negative temperature coefficient that becomes smaller as the temperature is higher. When the circuit draws a large amount of load current, the heating caused by the loss of the collector causes the temperature of the power tube Q1 to rise, causing the power tube Q1 overheating problem

Images