Power amplifier

Abstract

Provides thermally stable operation and low distortion power amplifiers. In this power amplifier, both ends of the resistor (RB) connected between the base terminal (B) of the bipolar transistor (Q1) and the base bias voltage supply terminal (VB) are paired via the first and second The high-frequency components of the impedance circuit (Z1, ZZ) form a bypass. Therefore, a part of the AC component of the base current flowing from the base bias supply terminal (VB) to the resistor (RB) is distributed to the bypass. Therefore, the actual effect is that the increase of the voltage drop on the resistor (RB) can be suppressed, the gain compression can be suppressed, and the power amplifier can operate with low distortion. In addition, the impedance of at least one of the first and second impedance circuits (Z1, ZZ) is open to the DC component and conductive to the AC component, so the base current can be suppressed by the voltage drop across the resistor (RB) increases with increasing temperature.

Description

technical field [0001] The present invention relates to a power amplifier with low distortion and high thermal stability in operation used in high frequency bands such as mobile phones. Background technique [0002] Bipolar transistors are typified by GaAs heterojunction bipolar transistors, and are used in power amplifiers such as mobile phones. [0003] In addition, bipolar transistors are devices with thermal positive feedback characteristics. Heat generation increases the base and collector currents. Therefore, for thermal stability, a circuit that suppresses the increase in collector current with temperature rise is generally added. [0004] Also, when bipolar transistors are used in the transmission power amplifier, in order to increase the output power, generally, a plurality of bipolar transistors are connected in parallel to obtain a predetermined output power. In this case, due to the temperature inhomogeneity among the individual transistors, the current is conce...

AI Technical Summary

Problems solved by technology

[0011] However, in the above conventional example, as the amplitude of the collector current increases, the increase in the base current increases the voltage drop across the resistors RB101 to RB10n, so the increase in the amplitude of the base current and the increase in the amplitude of the collector current cannot maintain a proportional relationship

This is so-called gain compression (ゲインコンプレツシヨン), which causes amplitude distortion in the amplifier

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