Semiconductor amplifier circuit and system

• US 6,366,172 B1
• Filed: 03/30/2001
• Issued: 04/02/2002
• Est. Priority Date: 07/07/1998
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kimura, Hiroshi, Hayashi, Joji
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/701,686
• Time in Patent Office: 368 Days
• Field of Search: 330/311, 333/217
• US Class Current: 330/311
• CPC Class Codes: H03F 1/223 with MOSFET's
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence
• CPC Class Codes: H03F 3/45179 using MOSFET transistors as the active amplifying circuit H03F3/45278 takes precedence
• CPC Class Codes: H03F 3/62 Two-way amplifiers

Abstract

The present invention has an objective of providing a semiconductor amplifier circuit having a cascode amplifier in which a negative characteristic of an output conductance is improved at least in a particular frequency band. A semiconductor amplifier 1 includes a cascode amplifier 500 having a transistor 101 and a transistor 102 which are cascaded, and improvement means for improving the negative characteristic of the output conductance G_out of the cascode amplifier 500 at least in a particular frequency band.

Claims

1. A semiconductor amplifier circuit, comprising:

a cascode amplifier having a first transistor and a second transistor which are cascaded; and

improvement means for improving a negative characteristic of an output conductance of the cascode amplifier at least in a particular frequency band,

wherein the improvement means,

comprises an element which functions as a resistor at least in a particular frequency band,

is configured to reduce a real number portion of a gate-source voltage of the second transistor,

and wherein the second transistor gate is coupled to the element such that the first transistor gate is independent of the second transistor gate and the element.

2. A semiconductor amplifier circuit according to claim 1, wherein the particular frequency band is a band of 100 MHz or more.

3. A semiconductor amplifier circuit according to claim 1, wherein the element functions as a resistor of 100Ω

or more at least in the particular frequency band.

4. A semiconductor amplifier circuit according to claim 1, wherein the element functions as a resistor of 10 kΩ

or less at least in the particular frequency band.

5. A semiconductor amplifier circuit according to claim 1, further comprising a high-pass filter connected to an output of the cascode amplifier.

6. A semiconductor amplifier circuit according to claim 5, wherein the high-pass filter is comprised of an inductor and a capacitor.