US 7,397,309 B2Granted

Bias circuit for a wideband amplifier driven with low voltage

AssigneeOki Electric Industry Co., Ltd.

InventorSatoru Tanoi

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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.

Claims4

Dependent claims

A bias circuit for an amplifier for providing a bias voltage to the amplifier comprising a ground, a first transistor, a second transistor, a first resistive load, and a first supply voltage, which are connected in series in this order, wherein

in the amplifier, a first bias voltage is provided to a gate electrode or a base of the first transistor, and a second bias voltage is provided to a gate electrode or a base of the second transistor,
said bias circuit comprising:
a third transistor having a gate electrode and a drain electrode, or a collector and a base, diode-connected, the drain electrode or collector of said third transistor providing the first bias voltage of the amplifier;
and
a fourth transistor, a fifth transistor and a second resistive load which are connected in series in this order, said first resistive load being connected to a second supply voltage, said fourth transistor having a gate electrode or a base connected to a drain electrode or a collector of said third transistor, said fifth transistor having a gate electrode and a drain electrode, or a base and a collector, diode-connected, the drain electrode or collector of said fifth transistor providing the second bias voltage;
wherein, with said second resistive load having resistance Rb and conducting a direct current Ib therethrough, and the first resistive load having resistance Ra and conducting a direct current therethrough equal to k×Ib, the resistance Ra is substantially equal to or more than Rb×(1/k), wherein k is a constant.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/359,370Filed 23 Feb 2006
Priority: JP 2005-08515724 Mar 2005
Published: US 2006/0226910 A112 Oct 2006
Granted: 8 Jul 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H03F 3/345
With semiconductor devices only: with field-effect devices
H03F 1/086
In transistor amplifiers: with FET's
H03F 1/223
By use of cascode coupling, i.e. earthed cathode or emitter stage followed by earthed grid or base stage respectively: with mosfet's
H03F 1/301
Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters: in MOSFET amplifiers