text: Patent US4649235 - Telephone circuit with a class-B amplifier output stage - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThe telephone amplifier of an audio transmission circuit comprises a class-B output stage as a result of which the required supply current of this amplifier is considerably lower than with prior art telephone amplifiers. A distorting voltage produced by the current signal in the supply current of the...http://www.google.com/patents/US4649235?utm_source=gb-gplus-sharePatent US4649235 - Telephone circuit with a class-B amplifier output stageAdvanced Patent SearchPublication numberUS4649235 APublication typeGrantApplication numberUS 06/680,430Publication dateMar 10, 1987Filing dateDec 11, 1984Priority dateDec 15, 1983Fee statusPaidAlso published asCA1219982A, CA1219982A1, DE3470267D1, EP0146185A2, EP0146185A3, EP0146185B1Publication number06680430, 680430, US 4649235 A, US 4649235A, US-A-4649235, US4649235 A, US4649235AInventorsPeter J. M. SijbersOriginal AssigneeU.S. Philips CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (6), Referenced by (4), Classifications (7), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetTelephone circuit with a class-B amplifier output stage
  US 4649235 AAbstract
  The telephone amplifier of an audio transmission circuit comprises a class-B output stage as a result of which the required supply current of this amplifier is considerably lower than with prior art telephone amplifiers. A distorting voltage produced by the current signal in the supply current of the glass-B output stage does not affect the output signal of the telephone amplifier because the input stage and the output stage each comprise their own setting circuits which produce mutually independent setting voltages.
  1. In a telephone circuit, having DC supply means:a telephone amplifier connected to said DC supply means and comprising an input stage; a class-B amplifier output stage connected to said input stage for furnishing an output signal; first DC operating level setting means connected to said input stage for setting a first DC operating level for said input stage; and second DC operating level setting means connected to said class-B amplifier output stage for setting a second DC operating level for said class-B amplifier output stage which is independent of said first DC operating level; said second level setting means comprising voltage divider means connected to said DC supply means and having a voltage divider tap, difference amplifier means having a first and second input and an output, said first input being connected to said voltage divider tap, and means for connecting said output to said second input and to said class-B amplifier output stage; whereby said output signal is substantially unaffected by current variations of said DC supply. 2. A telephone circuit combination as set forth in claim 1, wherein said means for connecting said output comprises a transistor having an emitter-base circuit connected between said output and said second input of said difference amplifier means and a collector connected to said DC supply.
  The invention has for its object to provide an audio transmission circuit of the type described in the opening paragraph for which the supply of direct current required is considerably less than the current required for these prior art audio transmission circuits, the other performances of this circuit being the same.
  FIG. 1 shows a telephone system in which the interconnection of the relevant elements of an audio transmission circuit according to the invention are illustrated, and
  FIG. 1 shows a portion of a telephone set connected to a telephone exchange 1. This telephone exchange 1 is symbolically denoted by a d.c. voltage source, which provides the supply for the telephone set, and two supply resistors arranged in series therewith. The connection between the telephone set and the telephone exchange is formed by the two-wire subscriber line 2, which is symbolically represented by two resistors each representing the resistance of one wire. In the telephone set the subscriber line 2 is connected to a rectifer 3, which is provided to render the set insensitive to polarity changes at the input terminals.
  Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3753137 *Mar 12, 1971Aug 14, 1973Licentia GmbhAmplifierUS3936614 *Sep 16, 1974Feb 3, 1976Stromberg-Carlson CorporationPBX ground start trunk interface for station carrier systemsUS4015212 *Oct 28, 1975Mar 29, 1977Sony CorporationAmplifier with FET having gate leakage current limitationUS4058775 *Feb 17, 1976Nov 15, 1977Rca CorporationOver-current prevention circuitry for transistor amplifiersUS4431972 *Sep 14, 1981Feb 14, 1984Pioneer Electronic CorporationPush-pull amplifierUS4446443 *May 20, 1982May 1, 1984Zenith Radio CorporationAmplifier having reduced power dissipation and improved slew rate* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS5229721 *Apr 6, 1992Jul 20, 1993Plantronics, Inc.Micropower amplifier/transducer driver with signal expansionUS5420919 *Jan 28, 1993May 30, 1995Sgs-Thomson Microelectronics S.A.Telephone line current modulatorUS6975172May 3, 2004Dec 13, 2005Peavey Electronics CorporationSmart voltage rail reduction audio amplifierUS20050242885 *May 3, 2004Nov 3, 2005Craynon Michael SSmart voltage rail reduction audio amplifier* Cited by examinerClassifications U.S. Classification379/348, 330/265, 379/395, 330/267International ClassificationH04M1/60Cooperative ClassificationH04M1/6016European ClassificationH04M1/60RLegal EventsDateCodeEventDescriptionMar 7, 1985ASAssignmentOwner name: U.S. PHILIPS CORPORATION 100 EAST 42ND ST., NEW YOFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SIJBERS, PETER J. M.;REEL/FRAME:004369/0732Effective date: 19850116Sep 4, 1990FPAYFee paymentYear of fee payment: 4Sep 1, 1994FPAYFee paymentYear of fee payment: 8Aug 26, 1998FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services