High-frequency amplifier and high-frequency multistage amplifier

• US 6,462,622 B1
• Filed: 11/19/2001
• Issued: 10/08/2002
• Est. Priority Date: 05/29/2001
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), SPX Corporation
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamauchi, Kazuhisa, Nakahara, Kazuhiko, Mori, Kazutomi, Takagi, Tadashi, Yamanaka, Koji
• Primary Examiner(s): Lee, Benny
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/988,326
• Time in Patent Office: 323 Days
• Field of Search: 330/302, 330/306, 330/310, 330/311, 330/144, 333/172, 333/81.R, 333/32
• US Class Current: 330/302
• CPC Class Codes: H03F 1/3205 in field-effect transistor amplifiers
• 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 3/1935 with junction-FET devices

Abstract

A T-type circuit having series resistors and a parallel resistor is arranged on the outside of an amplifier, a signal is amplified in the amplifier while stabilizing the signal by using the T-type circuit functioning as a stabilizing circuit, and the amplified signal is output. In this case, values of the series resistors and the parallel resistor of the T-type circuit are determined so as to set an output load impedance obtained by seeing the output side of the high-frequency amplifier from the amplifier to a value near to or slightly lower than a value of the conjugate complex impedance of an output impedance of the amplifier. Therefore, the output signal having a high output electric power and a low distortion can be obtained in the high-frequency amplifier while keeping a gain and a noise characteristic of the high-frequency amplifier.

Claims

1. A low noise high-frequency amplifier comprising:

an amplifier for amplifying an input signal; and

a stabilizing circuit, which is arranged only on an output side of the amplifier directly connected thereto and has a series resistor and a parallel resistor, for stabilizing the amplification of the input signal performed in the amplifier and outputting the amplified input signal.

2. The low noise high-frequency amplifier according to claim 1 wherein the stabilizing circuit is formed of a T-type circuit having a first series resistor, a second series resistor and the parallel resistor and having an impedance which is set in a value such that an output load impedance of the amplifier is a value near to or slightly lower than a value of the conjugate complex impedance of the output impedance of the amplifier.

3. The low noise high-frequency amplifier according to claim 1 wherein the stabilizing circuit is formed of a n-type circuit having the series resistor, a first parallel resistor and a second parallel resistor.

4. The low noise high-frequency amplifier according to claim 1 wherein the stabilizing circuit is formed of a ladder-type circuit having the series resistor and the parallel resistor.

5. The low noise high-frequency amplifier according to claim 1, further comprising:

a series inductor arranged between the amplifier and the stabilizing circuit; and

a parallel condenser arranged between the amplifier and the stabilizing circuit, both of which are directly coupled to the amplifier.

6. A low noise high-frequency multistage amplifier, comprising:

a specific high-frequency amplifier, arranged in a first stage, for amplifying an input signal; and

a general high-frequency amplifier, arranged in a stage following the first stage, for amplifying the input signal amplified by the specific high-frequency amplifier and outputting the amplified input signal as an output signal, and

the specific high-frequency amplifier comprises

an amplifier for amplifying the input signal; and

a stabilizing circuit, which is arranged only on an output side of the amplifier directly connected thereto and has a series resistor and a parallel resistor, for stabilizing the amplification of the input signal performed in the amplifier.

7. The low noise high-frequency multistage amplifier according to claim 6 wherein the stabilizing circuit of the specific high-frequency amplifier is formed of a T-type circuit having a first series resistor, a second series resistor and the parallel resistor having an impedance which is set in a value such that an output load impedance of the amplifier is a value near to or slightly lower than a value of the conjugate complex impedance of the output impedance of the amplifier.

8. The low noise low-frequency multistage amplifier according to claim 6 wherein the stabilizing circuit of the specific high-frequency amplifier is formed of a n-type circuit having the series resistor, a first parallel resistor and a second parallel resistor.

9. The low noise high-frequency multistage amplifier according to claim 6 wherein the stabilizing circuit of the specific high-frequency amplifier is formed of a ladder-type circuit having the series resistor and the parallel resistor.