US4049918A
Expired / Lapsed
US
⏱️ 0.0 years remaining
MPX stereo signal demodulator
Assignee: Sony Corp
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Filing: 1976-10-08
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Granted: 1977-09-20
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Expires: 1996-10-08
Abstract
Abstract A multiplex (MPX) stereo signal demodulator includes a first differential amplifier supplied with a composite stereo signal and second, third differential amplifiers cascode-connected to the first differential amplifier and supplied with a 38 KHz subcarrier signal so as to obtain, by demodulation, a pair of audio signals as the multiplying results of the composite and subcarrier signals. A fourth differential amplifier supplied with the composite stereo signal, the input level of which is adjustable, is provided and the output signal therefrom is mixed with the pair of audio signals through a current mirror circuit so as to compensate the separation ratio therebetween.
Inventors
- 👤 Misuo Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:44
CPC Classifications
H; H03; H03D; H03D1/00; H03D1/22; H03D1/2209; H03D1/2227
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
291 words
An MPX stereo signal demodulator comprising: A. a direct voltage source; B. a first differential amplifier including at least a first pair of transistors and a common emitter impedance connected to a reference voltage point; C. a second differential amplifier including at least a second pair of transistors with the emitters thereof connected to each other and to the collector of one of the transistors of said first differential amplifier; D. a third differential amplifier including at least a third pair of transistors with the emitters thereof connected to each other and to the collector of the other transistor of said first differential amplifier; E. coupling circuit means for coupling the collector of one of the transistors of said second differential amplifier to a first connection point comprising the collector of one of the transistors of said third differential amplifier and coupling the collector of the other transistor of said second differential amplifier to a second connection point comprising the collector of the other transistor of said third differential amplifier, respectively, said connection point comprising a pair of signal output terminals; F. a fourth differential amplifier including at least a fourth pair of transistors and a common emitter impedance connected to the reference voltage point; G. current mirror circuit means connected between said direct voltage source and collector circuits of said second, third and fourth differential amplifiers; H. signal input means for applying a composite stereo signal to said first and fourth differential amplifiers and for applying a subcarrier signal to said second and third differential amplifiers, respectively; and I. means for varying the composite signal levels applied to said first and fourth differential amplifiers, relatively, so as to adjust separation characteristics between the output signals at said signal output terminals.
Claim 2
Dependent Claim
291 words
An MPX stereo signal demodulator comprising: A. a direct voltage source; B. a first differential amplifier including at least a first pair of transistors and a common emitter impedance connected to a reference voltage point; C. a second differential amplifier including at least a second pair of transistors with the emitters thereof connected to each other and to the collector of one of the transistors of said first differential amplifier; D. a third differential amplifier including at least a third pair of transistors with the emitters thereof connected to each other and to the collector of the other transistor of said first differential amplifier; E. coupling circuit means for coupling the collector of one of the transistors of said second differential amplifier to a first connection point comprising the collector of one of the transistors of said third differential amplifier and coupling the collector of the other transistor of said second differential amplifier to a second connection point comprising the collector of the other transistor of said third differential amplifier, respectively, said connection point comprising a pair of signal output terminals; F. a fourth differential amplifier including at least a fourth pair of transistors and a common emitter impedance connected to the reference voltage point; G. current mirror circuit means connected between said direct voltage source and collector circuits of said second, third and fourth differential amplifiers; H. signal input means for applying a composite stereo signal to said first and fourth differential amplifiers and for applying a subcarrier signal to said second and third differential amplifiers, respectively; and I. means for varying the composite signal levels applied to said first and fourth differential amplifiers, relatively, so as to adjust separation characteristics between the output signals at said signal output terminals.
Claim 3
Dependent Claim
37 words
An MPX stereo signal demodulator according to claim 1, further comprising first direct voltage biasing means connected to provide the same direct biasing voltage to the bases of the transistors of said first and fourth differential amplifiers.
Claim 4
Dependent Claim
58 words
An MPX stereo signal demodulator according to claim 2, further comprising second direct voltage biasing means; and a pair of load impedances connected between said signal output terminals and said second direct voltage biasing means, said second direct voltage biasing means being connected between the reference voltage point and the connection point of said pair of load impedances.
Claim 5
Dependent Claim
66 words
An MPX stereo signal demodulator according to claim 3 comprising a third direct voltage biasing means, said first differential amplifier comprising first, second and third transistors and said fourth differential amplifier comprising fourth, fifth and sixth transistors, each of said third and sixth transistors forming a common emitter impedance, respectively, the bases thereof being connected to said third DC biasing means to be equally biased thereby.
Claim 6
Dependent Claim
57 words
An MPX stereo signal demodulator according to claim 4, in which said second differential amplifier comprises seventh and eighth transistors and said third differential amplifier comprises ninth and tenth transistors, both collectors of said seventh and ninth transistors being connected to each other, and both collectors of said eighth and tenth transistors being connected to each other.
Claim 7
Dependent Claim
160 words
An MPX stereo signal demodulator according to claim 5, in which said current mirror circuit means comprises: A. an eleventh transistor with the emitter connected to said direct voltage source and the collector connected to the connection point of collectors of said seventh and ninth transistors; B. a twelfth transistor with the emitter connected to said direct voltage source and the collector connected to the connection point of collectors of said eighth and tenth transistors; C. a thirteenth transistor, the bases of said eleventh and twelfth transistors being connected to each other and to an emitter of the thirteenth transistor, the collector of the thirteenth transistor connected to the reference voltage point; and D. a fourteenth transistor having its emitter connected to said direct voltage source and its collector connected to the collector of said fourth transistor and the base of said thirteenth transistor, and the base of the fourteenth transistor being connected to the emitter of said thirteenth transistor.
Claim 8
Dependent Claim
91 words
An MPX stereo signal demodulator according to claim 6, in which said first direct voltage biasing circuit comprises: A. a fifteenth transistor with the collector thereof connected to said direct voltage source; B. a first resistor connecting the emitter of the fifteenth transistor to the reference voltage point; C. a second resistor connecting the base of said fifteenth transistor to said direct voltage source; and D. a series connection comprising at least one diode and a Zener diode connected between the base of said fifteenth transistor and the reference voltage point.
Claim 9
Dependent Claim
50 words
An MPX stereo signal demodulator according to claim 7 comprising third, fourth, fifth and sixth resistors of equal resistance values, each of the bases of said first, second, fourth and fifth transistors being connected to the emitter of said fifteenth transistor through said third, fourth, fifth, and sixth resistors, respectively.
Claim 10
Dependent Claim
79 words
An MPX stereo signal demodulator according to claim 8 comprising a fixed resistor and a variable resistor, said signal input means being connected to the base of one of the transistors of said first differential amplifier to supply the composite stereo signal thereto through said fixed resistor, and said signal input means being connected to the base of one of the transistors of said fourth differential amplifier to supply the same composite stereo signal thereto through said variable resistor.
Claim 11
Dependent Claim
25 words
An MPX stereo signal demodulator according to claim 9, in which each of said first, second, fourth and fifth transistors comprises Darlington-connected pair of transistors.
Claim 12
Dependent Claim
15 words
An MPX stereo signal demodulator according to claim 3, further including muting control circuit means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-09-19 | 1981-03-21 | 1981-09-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-19 | 1985-03-21 | 1985-09-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-19 | 1989-03-21 | 1989-09-20 | $7700.00 | Window Closed / Lapsed |