Pulse width modulated signal amplifier

• US 4,021,745 A
• Filed: 12/16/1975
• Issued: 05/03/1977
• Est. Priority Date: 12/18/1974
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yoshida, Tadao, Suzuki, Tadao
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US05/641,244
• Time in Patent Office: 504 Days
• Field of Search: 330/9, 330/10, 330/75, 330/207 A, 329/106
• US Class Current: 330/10
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03K 7/02 Amplitude modulation, i.e. PAM

Abstract

A pulse width modulated signal amplifier includes a first input terminal supplied with a rectangular wave signal as a carrier, a second input terminal supplied with a modulating signal, such as an audio signal, an integrator supplied with both the rectangular wave signal and the modulating signal, a high gain amplifier receiving the output of the integrator, a low pass filter receiving the output of the high gain amplifier and producing a demodulated signal corresponding to the modulating signal and which is supplied to an output terminal, and a negative feedback circuit connected between the output of the high gain amplifier and the input of the integrator.

Claims

1. A pulse width modulated signal amplifier comprising first and second input terminals for receiving a rectangular waveform signal as a carrier and a modulating signal, respectively;

integrating means having an input and an output;

summing means receiving said rectangular waveform signal and said modulating signal for supplying the sum of said rectangular waveform signal and said modulating signal to the input of said integrating means;

high gain amplifying means having an input connected to said output of said integrating means and an output;

a low pass filter connected to said output of the high gain amplifying means for producing a demodulated signal;

an output terminal receiving said demodulated signal from said low pass filter; and

a negative feedback circuit connected between said output of the high gain amplifying means and said input of said integrating means to provide a negative feedback signal at said input of the integrating means which is substantially in phase with a signal provided at said output of the high gain amplifiying means and smaller than the rectangular waveform signal so that the modulation ratio of said rectangular waveform signal may be selected as high as 100 percent.

2. A pulse width modulated signal amplifier according to claim 1;

in which said summing means includes first and second resistors connected at one end to said first and second input terminals, respectively, and having their other ends connected together to said input of the integrating means.

3. A pulse width modulated signal amplifier according to claim 2;

in which said negative feedback circuit consists of a third resistor connected between said output of the high gain amplifying means and said input of the integrating means.

4. A pulse width modulated signal amplifier according to claim 1;

in which said negative feedback circuit consists of a resistor connected between said output of the high gain amplifying means and said input of the integrating means.

5. A pulse width modulated signal amplifier comprising first and second input terminals for receiving a rectangular waveform signal as a carrier and a modulating signal, respectively;

integrating means having an input and an output;

summing means receiving said rectangular waveform signal and said modulating signal for supplying the sum of said rectangular waveform signal and said modulating signal to the input of said integrating means;

high gain amplifying means having an input connected to said output of said intergrating means and an output for producing a pulse width modulated signal having a predetermined duty ratio in the absence of a modulating signal, said duty ratio being varied from said predetermined ratio as a function of said modulating signal;

a low pass filter connected to said output of the high gain amplifying means for producing a demodulated signal;

an output terminal receiving said demodulated signal from said low pass filter; and

a negative feedback circuit connected between said output of the high gain amplifying means and said input of said integrating means to provide a negative feedback signal at said input of the integrating means which is substantially in phase with said pulse width modulated signal provided at said output of the high gain amplifying means and smaller than the rectangular waveform signal so that the modulation ratio of said rectangular waveform signal may be selected as high as 100 percent.

6. A pulse width modulated signal amplifier according to claim 5;

in which said negative feedback circuit consists of a resistor connected between said output of the high gain amplifying means and said input of the integrating means.