Doherty amplifier

• US 20060055458A1
• Filed: 12/17/2003
• Published: 03/16/2006
• Est. Priority Date: 01/09/2003
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Shiikuma, Kazumi, Mizoguchi, Junichi
• Granted Patent: US 7,295,064 B2
• Time in Patent Office: Days
• US Class Current: 330/124.R
• CPC Class Codes: H03F 1/0288 using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
• CPC Class Codes: H03F 1/3276 using the nonlinearity inherent to components, e.g. a diode

Abstract

The present invention is intended to provide a Doherty amplifier that can accomplish a linear amplifying and a power combining operation closer to the ideal in a simple configuration. The configuration comprises gain compensator 6 that is composed of a parallel circuit made of an anti-parallel diode and a resistor that is disposed at a position ahead of peak amplifier 4 included in the Doherty amplifier. Setting the gain in gain compensator 6 allows peak amplifier 4 to be compensated for the operation characteristic, when peak amplifier 4 is operating, based on the gm characteristic of peak amplifier 4.

Claims

1. canceled

2. canceled

3. A Doherty amplifier comprising:

an input terminal;

input branching means for distributing a signal applied from said input terminal to a first path and a second path;

a carrier amplifier for amplifying a signal distributed to the first path by said input branching means;

a peak amplifier for amplifying a signal of a predetermined level or higher among signals distributed to the second path by said input branching means;

output combining means for combining an output of said carrier amplifier with an output of said peak amplifier; and

a gain compensator disposed at a position ahead of said peak amplifier in the second path for changing a gain in accordance with the level of an input signal in order to correct the level of the signal distributed to the second path,

said carrier amplifier and said peak amplifier being devices having the same characteristics,

said peak amplifier having a gain smaller than an ideal gain,

wherein said gain compensator has a larger gain, when a signal equal to or higher than the predetermined level is applied, than a gain when a signal lower than the predetermined level is applied, said gain being set based on a transfer conductance of said peak amplifier.

6. The Doherty amplifier according to claim 3, wherein said gain compensator comprises a parallel circuit composed of an anti-parallel diode and a resistor, or a parallel circuit composed of a diode and a resistor, or an FET, or a bipolar transistor.

7. The Doherty amplifier according to claim 3, wherein said carrier amplifier and said peak amplifier are each composed of an FET, and said gain compensator compensates said peak amplifier for a gm characteristic.

4. canceled

5. canceled