Bias circuit for a wideband amplifier driven with low voltage

Abstract

An amplifier includes a ground, first and second MOS transistors, a first resistive load and a supply voltage, which are connected in series in this order. A bias circuit provides first and second bias voltages to the gate electrodes of the first and second transistors, respectively. The bias circuit includes a third MOS transistor having its gate and drain electrode diode-connected. The drain electrode of the third transistor provides the first bias voltage of the amplifier. The bias circuit further includes fourth and fifth MOS transistors, and a second resistive load, which are connected in series in this order. The second resistive load is connected to the supply voltage. The fourth transistor has its gate electrode connected to the drain electrode of the third transistor. The fifth transistor has its gate and drain electrodes diode-connected. The drain electrode of the fifth transistor provides the second bias voltage.

Description

technical field [0001] The present invention relates to a bias circuit for supplying a bias voltage to a high-frequency amplifying circuit. This circuit can also be applied to a bias circuit for an amplifying circuit called UWB (Ultra Wideband) that requires a wide-band operation of 500 MHz or more , can work with low voltage and low power consumption. Background technique [0002] As a conventional example of a high-frequency amplifier circuit used in a narrow band, there is an example shown in Non-Patent Document 1, for example. Examples of cascode amplifier circuits for improving high-frequency characteristics are shown on p.164 to 166 of Non-Patent Document 1, and examples of amplifier circuits exemplifying element constants are shown on p.288 to 292. [0003] In addition, as a conventional example of a high-frequency amplifier circuit used in a broadband, there is an example shown in Non-Patent Document 2, for example. Regarding the quality coefficient as an index ind...

AI Technical Summary

Problems solved by technology

However, this circuit has a problem that stable amplification cannot be obtained if the power supply voltage is lowered.

That is, in the conventional circuit configuration, it is difficult to achieve both an amplification operation with a sufficiently high gain in a wide frequency band and an amplification operation at a low power supply voltage.

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