High-frequency amplifier circuit having a directly-connected bias circuit

Abstract

A high-frequency amplifier circuit includes an amplifying transistor and a bias circuit directly connected to said amplifying transistor. The bias circuit includes a bias transistor having a control terminal and an inductor coupled to the control terminal, and the bias transistor also has an output terminal directly connected to the amplifying transistor. A resistor is connected in series with the inductor, and the series-connected components are connected in the circuit between the control terminal and a power supply terminal. By providing an inductor in the amplifier in this manner, loading effects on the amplifying transistor at high frequencies is substantially reduced.

Description

FIELD OF THE INVENTION[0001] The invention is in the field of transistor amplifier circuits, and relates more particularly to high-frequency amplifier circuits and bias circuits for such amplifier circuits.BACKGROUND OF THE INVENTION[0002] In high-frequency amplifier circuits, the output stage is typically a bipolar transistor connected in a common-emitter configuration, biased with either a voltage source or a current source providing a bias signal at the base of the output stage transistor.[0003] In IC technology, a straightforward way of biasing the output stage is to use a current-mirror circuit where the output stage is part of the current-mirror circuit. The quiescent DC current in the output stage can be directly controlled by a constant current in the current-mirror circuit. Typically, the bias of the amplifying transistor is provided by the current-mirror circuit through a resistor. However, the use of a resistor results in an increase in power loss in the circuit. This los...

AI Technical Summary

Benefits of technology

[0006] It is therefore an object of the invention to provide a high-frequency amplifier circuit in which a bias circuit is provided which minimizes mismatch, minimizes power loss due to parasitic resistance in an inductor, and permits an external component to be connected with only a single bonding pad.

[0010] High-frequency amplifier circuits in accordance with the present invention offer a significant improvement in that mismatch effects and power losses due to parasitic resistance are minimized and the connection of an external component such as an inductor is simplified.

Problems solved by technology

However, the use of a resistor results in an increase in power loss in the circuit.

This loss may be quite significant when a large current flows through the resistor.

However, this is not a complete solution to the problem, since parasitic resistance from the inductor can still cause a power loss and furthermore, it may cause a mismatch between the transistor pair in the current-mirror circuit due to the parasitic resistance.

This is relatively undesirable, since bonding pads are always at a premium in IC design.

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