Noise filter circuit

• US 7,205,831 B2
• Filed: 02/17/2003
• Issued: 04/17/2007
• Est. Priority Date: 04/23/2002
• Status: Expired due to Fees

• Current Assignee: Nanopower Solutions Incorporated
• Original Assignee: Nanopower Solutions Incorporated
• Inventors: Shinichi, Akita
• Primary Examiner(s): LE, DINH THANH
• Application Number:
  US10/512,102
• Publication Number:
  US 20050156663A1
• Time in Patent Office: 1,520 Days
• Field of Search: 327551-559, 327531-532
• US Class Current: 327/551
• CPC Class Codes: G05F 1/467 Sources with noise compensation

Abstract

There is provided a noise canceling circuit that includes a first source terminal, a second source terminal, an output terminal, a reference voltage generator for generating a reference voltage, a bias current generator for generating a bias current determining an operating current, a voltage-current generator for generating an output of a power circuit, a voltage divider for detecting a fluctuation of an output voltage at the output terminal, and an error amplifier for amplifying an error voltage between said reference voltage and an output voltage from the voltage divider.

Claims

1. A noise canceling circuit, comprising:

a first source terminal;

a second source terminal;

an output terminal;

a reference voltage generator for generating a reference voltage, having an input connected to said first source terminal, and an input connected to said second source terminal, and an output;

a bias current generator for generating a bias current determining an operating current, having a first source input, a second source input, and an output;

a voltage-current generator for generating an output of a power circuit, having a first input connected to said first source terminal, a second input, and an output connected to said output terminal;

a voltage divider for detecting a fluctuation of an output voltage at the output terminal, having an input connected to said second source terminal, an input connected to said output terminal, and an output; and

an error amplifier for amplifying an error voltage between said reference voltage and an output voltage from said output of said voltage divider, having an input connected to said first source terminal, an input connected to said second source terminal, an input connected to said output of said reference voltage generator, an input connected to said output of said bias current generator, an input connected to said output of said voltage divider, and an output connected to said second input of said voltage-current generator,

wherein said error amplifier comprises an input part, a load part, a noise suppression part, and a phase compensation capacitor,

wherein said input part comprises a pair of first type semiconductor elements,

wherein said load part comprises a pair of second type semiconductor elements, and

wherein said noise suppression part (i) is disposed between said input part and said load part, (ii) has an input connected to said first source terminal, and (iii) comprises a pair of the first type semiconductor elements of different dimension in length or width.

2. A noise canceling circuit according to claim 1, further comprising:

a canceling signal generator containing a capacitance different from said phase compensation capacitor,

wherein said capacitance is connected to (i) said output of said voltage-divider, and (ii) the first source terminal or a circuit node changing with a same phase as a voltage at the first source terminal.

3. A noise canceling circuit according to claim 1, further comprising:

a canceling signal generator containing a capacitance different from said phase compensation capacitor,

wherein said capacitance is connected to (i) said output of said voltage-divider, and (ii) the first source terminal or a circuit node changing with a same phase as a voltage at the first source terminal.

4. A noise canceling circuit, comprising:

a first source terminal;

a second source terminal;

an output terminal;

a reference voltage generator for generating a reference voltage and generating a bias current determining an operating current, having an input connected to said first source terminal, an input connected to said second source terminal, and a reference voltage output;

a voltage-current generator for generating an output of a power circuit, having a first input connected to said first source terminal, a second input, and an output connected to said output terminal;

a voltage divider for detecting a fluctuation of an output voltage at the output terminal, having an input connected to said second source terminal, an input connected to said output terminal, and an output; and

an error amplifier for amplifying an error voltage between said reference voltage and an output voltage from said output of said voltage divider, having an input connected to said first source terminal, an input connected to said second source terminal, an input connected to said reference voltage output, an input connected to said output of said voltage divider, and an output connected to said second input of said voltage-current generator,

wherein said error amplifier comprises an input part, a load part, a noise suppression part, and a phase compensation capacitor,

wherein said input part comprises a pair of first type semiconductor elements,

wherein said load part comprises a pair of second type semiconductor elements, and

wherein said noise suppression part (i) is disposed between said input part and said load part, (ii) has an input connected to said first source terminal, and (iii) comprises a pair of the first type semiconductor elements of different dimension in length or width.