# US 4,393,353 A · Negative feedback amplifying circuit having voltage negative feedback and current negative feedback circuits

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- Number: US 4,393,353 A
- Document ID: US4393353A
- Status: Granted
- Kind: A
- Application number: 06/191,355
- Filed: 1980-09-26
- Granted: 1983-07-12
- Earliest claimed: 1979-09-28
- Assignees: Victor Company of Japan, Ltd.
- Inventors: Hiroyasu Minagawa
- Web page: https://patentgrep.com/patent/US4393353A

## CPC

- H04R 3/002: {Damping circuit arrangements for transducers, e.g. motional feedback circuits}
- H03F 1/34: Negative-feedback-circuit arrangements with or without positive feedback (H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence {; for rejection of common mode signals H03F3/45479})
- H03F 3/183: with semiconductor devices only
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)
- H03F: AMPLIFIERS

## Abstract

A negative feedback amplifying circuit comprises an amplifier connected to a load, a voltage negative feedback circuit which negatively feeds back the output voltage of the amplifier to the input side of the amplifier maintaining a frequency selection characteristic, and a current negative feedback circuit which negatively feeds back a current signal obtained by detecting the current flowing through the load to the input side of the amplifier maintaining a frequency selection characteristic. The voltage negative feedback circuit has a frequency selection characteristic comprising a dip at a specific frequency f.sub.0. On the other hand, the current negative feedback circuit has a frequency characteristic comprising a peak at a specific frequency f.sub.0.

## Claims

### Claim 1

A negative feedback amplifying circuit comprising:
(a) an amplifier having positive and negative inputs, the output of said amplifier being coupled to a load comprising a speaker;
(b) a resistor connected in series with said speaker;
(c) a voltage negative feedback circuit for feeding back the output voltage of said amplifier to the negative input of said amplifier; and
(d) a current negative feedback circuit for feeding back a signal, which is a function of the potential difference between both the ends of said resistor, to the negative input of said amplifier, said voltage negative feedback circuit having a frequency selection characteristic having a dip at a specific frequency which is equal to the minimum resonance frequency due to the mechanical impedance of said speaker, and said current negative feedback circuit having a frequency selection characteristic having a peak at said specific frequency.

### Claim 2 (depends on 1)

A negative feedback amplifying circuit as claimed in claim 1, in which the frequency selection characteristics of said voltage negative feedback circuit and said current negative feedback circuit are selected so that at said specific frequency, the level attenuation quantity of said voltage negative feedback circuit is substantially equal to the level intensification quantity of said current negative feedback circuit.

### Claim 3 (depends on 1)

A negative feedback amplifying circuit as claimed in claim 1, in which both said voltage negative feedback circuit and said current negative feedback circuit contain series resonance circuits having a resonance frequency equal to said specific frequency.

### Claim 4 (depends on 3)

A negative feedback amplifying circuit as claimed in claim 3, in which each of said series resonance circuits contain a simulated inductance circuit comprising a semiconductor circuit so as to include an inductance component.

### Claim 5 (depends on 4)

A negative feedback amplifying circuit as claimed in claim 4, in which said simulated inductance circuit comprises variable resistors capable of varying said resonance frequency.

### Claim 6 (depends on 4)

A negative feedback amplifying circuit as claimed in claim 4, further comprising:
(a) a first lowpass filter, within said voltage negative feedback circuit, provided between said simulated inductance circuit and the output side of said amplifier;
(b) a path parallel with said simulated inductance circuit and said first lowpass filter within said voltage negative feedback circuit, for negatively feeding back the frequency components cut off by said first lowpass filter from said amplifier; and
(c) a second lowpass filter within said current negative feedback circuit provided between said simulated inductance circuit and said resistor.