Amplifier

Abstract

The present invention provides an apparatus for compensating distortion of a multi-stage amplifier having gain extension characteristics. The present invention also provides a method for biasing the amplification stages closer to a Class B regime exhibiting higher power added efficiency at low output, so as to have gain extension characteristics in all stages of a multistage amplifier. The amplifier of the present invention has the characteristic of gain expansion, and it shows that the gain increases with the increase of the input power or output power within a certain range of input power or output power. The amplifier is characterized in that the emitter-grounded amplifier circuit comprising a first bipolar transistor has a base terminal which passes through a first impedance element which does not block direct current and an input matching circuit and a first diode which provides a bias voltage. The cathode is connected, while the first diode has an anode connected to a reference power supply that presents a very low impedance at high frequencies.

Description

technical field [0001] The present invention relates to an amplifier, and more particularly to an amplifier used in radio communication for controlling output power over a wide range, which amplifies input power by a plurality of transistors connected in a multi-stage manner to generate amplified power . Background technique [0002] Power amplifiers using bipolar transistors with grounded emitters integrally require a base bias circuit that operates close to a regulated power supply. A regulated power supply is more suitable for biasing circuits than a rectified current source for reasons explained below. [0003] Consider the case of a radio frequency (RF) input applied to a grounded emitter bipolar transistor whose base is provided with a bias from a regulated power supply. This grounded-emitter bipolar transistor exhibits small-signal operation when the input power is small enough that its collector current is substantially equal to the so-called bias current flowing t...

AI Technical Summary

Problems solved by technology

The fifth conventional amplifier has the fifth problem that the injection amount must be adjusted by feedback, feedforward, etc., because the optimal injection amount depends on the input amplitude

[0069] As the third problem mentioned above, in order to increase the efficiency of additional power at low output, the first to third conventional amplifiers have disadvantages in that when they are used with a bias close to the class B state, due to the gain extension while the signal is distorted

[0070] Also, as the fourth problem mentioned above, the fourth conventional amplifier has the disadvantage of not being able to use amplification stages, and due to the third problem mentioned above, all stages exhibit better power added efficiency at low output

[0071] Then, the fifth problem mentioned above, the fifth conventional amplifier also has the disadvantage that due to the dependence of the optimum injection amount on the input amplitude, in differential frequency signal injection, the injection amount must be adjusted by feedback, feedforward, etc.

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