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WO1993016524A1 - Circuit d'amplificateur - Google Patents

Circuit d'amplificateur Download PDF

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Publication number
WO1993016524A1
WO1993016524A1 PCT/GB1993/000280 GB9300280W WO9316524A1 WO 1993016524 A1 WO1993016524 A1 WO 1993016524A1 GB 9300280 W GB9300280 W GB 9300280W WO 9316524 A1 WO9316524 A1 WO 9316524A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
amplifier
output
circuit
input
Prior art date
Application number
PCT/GB1993/000280
Other languages
English (en)
Inventor
Barry Elliot Porter
Original Assignee
Audio Solutions Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Audio Solutions Limited filed Critical Audio Solutions Limited
Priority to EP93904188A priority Critical patent/EP0626111A1/fr
Publication of WO1993016524A1 publication Critical patent/WO1993016524A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback

Definitions

  • This invention relates to an amplifier circuit and particularly, but not exclusively, to an amplifier 5 circuit for amplifying signal components in the audio ft frequency range.
  • the output signal of an amplifier usually includes unwanted distortion components.
  • 10 components are mainly harmonic components caused by non ⁇ linear characteristics within the amplifier and inter- modulation components caused by inter- modulation between signals within the amplifier. In order to reduce the distortion components in the output signal, it is well
  • Attenuator 20 amplifier will be determined primarily by the attenuator.
  • an attenuator may be constructed from components having substantially linear characteristics, such a feedback circuit is effective to reduce distortion components to a low but measurable level. It would, however, be desirable
  • an amplifier circuit comprising a main amplifier section having an input for receiving an input signal and an output for delivering an output signal, and a feedback circuit comprising means for attenuating the output signal to the level of the input signal to produce an attenuated signal, means for obtaining the difference between the input signal and the attenuated signal to produce a difference signal, means for amplifying the difference signal to produce a feedback signal, and means for supplying the feedback signal to the input of the main amplifier section as a negative feedback signal.
  • the feedback circuit includes means for correcting the phase of the input signal prior to supplying the input signal to the difference obtaining means.
  • the gain of the amplifying means expressed as the ratio of output voltage to the input voltage is greater for DC signal components than for signal components in the audio frequency range.
  • the amplifier circuit includes a second feedback circuit comprising means for attenuating the output signal to produce a second attenuated signal and means for supplying said second attenuated signal to the input of the main amplifier as a negative feedback signal.
  • Figure 1 is a circuit diagram of an amplifier circuit according to a first embodiment of this invention.
  • FIGS. 2 and 3 together form a circuit diagram of a second amplifier circuit according to a second and preferred embodiment of this invention. MODES OF CARRYING OUT THE INVENTION
  • an amplifier circuit for amplifying signals in the audio frequency range comprising a main amplifier section in the form of a single power amplifier 12, a first feedback circuit 14 and a second feedback circuit comprising resistors Rl, R2.
  • the non-inverting input of amplifier 12 is connected to a terminal 16 receiving an input signal.
  • the output of amplifier 12 is connected to an output terminal 18 for delivering an output signal and the terminal 18 is connected to the input of a loudspeaker 20.
  • resistors Rl and R2 are connected between the output of amplifier 12 and ground and the junction of these two resistors is connected to the inverting input of amplifier 12.
  • resistors Rl, R2 function to attenuate the output signal and to supply the attenuated signal to amplifier 12 as a negative feedback signal. Consequently, the gain of amplifier 12 is determined by the attenuator comprising resistors Rl, R2.
  • the first feedback circuit includes a pair of resistors R3, R4 connected between terminal 18 and ground and which also function as an attenuator. The junction of these two resistors is connected through a variable resistor R5 and a further resistor R6 to the inverting input of operational amplifier 22. The output of amplifier 22 is connected through a capacitor Cl and a resistor R7 to its inverting input.
  • the resistors R3 and R4 are arranged to attenuate the output signal by a factor which is equal to the amplification factor of amplifier 12 as determined by resistors Rl, R2.
  • the first feedback circuit 14 also includes a phase correction circuit comprising resistor R8, capacitor C2 and resistor R9, connected in a series between terminal 16 and earth, and variable capacitor C3 connected in parallel with resistor R9.
  • the junction of capacitor C2 and resistor R9 is connected to the non-inverting input of amplifier 22.
  • Resistor R8 has a small resistance value compared with resistor R9 and capacitor C2 has a low impedance in the audio frequency range.
  • the phase correction circuit is designed to compensate for phase changes occurring in amplifier 12 so that the signals supplied to the non-inverting and inverting inputs of amplifier 22 are in phase.
  • the phase change occurring in amplifier 12 is only a few degrees.
  • Capacitor C3 may be adjusted so as to bring the two signals as closely into phase with each other as possible.
  • the resistor R5 may be adjusted to ensure that the levels of the two signals are as close as possible.
  • the amplifier 22 is configured as a difference amplifier and its output signal represents the difference between the input signal and the output signal attenuated to the level of the input signal. This difference signal represents the distortions present in the output signal and introduced by amplifier 12.
  • the output of amplifier 22 is connected through a resistor RIO to the inverting input of an operational amplifier 23, the output of which is connected through a feedback resistor Rll to its inverting input.
  • the output of amplifier 23 also represents distortion components present at the output of amplifier 12.
  • the distortion components are greatly amplified in comparison with the distortion components present in the output signal at terminal 18.
  • the output of amplifier 23 is supplied as a feedback signal through a resistor R12 to the inverting input of amplifier 12.
  • the output of amplifier is supplied to amplifier 12 as a negative feedback signal.
  • the first feedback circuit 14 functions to greatly reduce the level of the distortion components appearing at the output of amplifier 12.
  • the amplifier circuit 10 is designed to be DC coupled both to the input signal and to the loudspeaker 20.
  • the first feedback circuit 14 also functions to reduce any DC bias in the output of amplifier 12 to a negligible level.
  • capacitor C2 blocks any DC component present in the input signal.
  • the capacitance value of capacitor Cl is selected so that amplifier 22 has a much greater gain for DC components than for components in the audio frequency range.
  • the combined gain of amplifiers 22 and 23 for DC components is at least 100 and, preferably, in excess of 1000.
  • any DC bias present in the output signal of amplifier 12 is supplied to its input after great amplification as a negative feedback signal. Consequently, any DC bias in the output of amplifier 12 is .-educed t ⁇ a negligible leve..
  • the amplifier circuit has an input terminal 30 for receiving an input signal, an output terminal 32 for delivering an output signal and which may be connected to a loudspeaker, a main amplifier section comprising a first stage 32, second stage 34 and a third stage > , a first feedback circuit 38, and a second feedback circuit 40.
  • the amplifier circuit has a positive supply terminal 42 connected through a fuse 44 to a line 46.
  • Line 46 is connected to earth through a capacitor CIO and to a positive supply line 48 through a diode Dl.
  • the amplifier circuit also has a negative supply terminal 50 connected through a fuse 52 to a line 54.
  • Line 54 is connected through a capacitor Cll to earth and through a diode D2 to a negative supply line 56.
  • the positive and negative supply lines 48 and 56 are connected, respectively, to earth through capacitors C12, C13.
  • the first stage comprises a pair of FET type transistors Ql, Q2, five further transistors Q3 to Q7, resistors R20 to R31, capacitors C15, C16, diodes D3 to D5, and a 12 volt zener diode ZD1.
  • the input signal is connected through a resistor R21 to the base of transistor Ql.
  • the first amplifying stage is configured as a differential amplifier and the base of transistor Ql is the non-inverting input.
  • the base of transistor of Q2 is the inverting input.
  • the output of the first stage 32 is produced between the collectors of transistors Q3 and Q6 and this output is supplied to the second stage 34.
  • the second stage comprises transistors Q8 to
  • the output of the second stage is produced between the anode and cathode of zener diode ZD2 and supplied to the third stage on lines 57, 58.
  • the third stage comprises transistors Q14 to
  • Transistors Q24 and Q25 are of the MOSFET type.
  • the third stage is configured as a push-pull amplifier and transistors Q22 and Q23 drive the output transistors Q24 and Q25.
  • the output signal is present at the junction of resistors R57 and R58 and this junction is connected to the output terminal 32.
  • Transistors Q14 to Q19 together with associated components function as an output biasing arrangement.
  • Transistors Q20 and Q21 together with associated components provide protection against a short circuit across the output terminal 32.
  • the output terminal 32 is connected through resistors R59 and R60 and capacitor C26 to earth. Resistor 59 is bridged by capacitor C27. The junction of resistors R59 and R60 is connected to the base of transistor Q2 of the first stage 32.
  • the second feedback circuit 40 attenuates the output signal and supplies the resulting attenuated signal to the first stage as a negative feedback signal. Consequently, the overall gain of the stages 32, 34, 36 of the main amplifying section is determined by the second feedback circuit 40.
  • the output terminal 32 is connected through a variable resistor R61, a resistor R62, a resistor R63 and a capacitor C28 to earth.
  • Resistors R61 tc R63 together with capacitor C28 function as an attenuator and function to attenuate the output signal present at output terminal 32 to the level of the input signal at terminal 30.
  • the attenuated signal which appears at the junction of resistors R62 and R63, is connected to the inverting input of an operational amplifier 60.
  • the output of amplifier 60 is connected to its input through a capacitor C30 and resistor R64, resistor R64 being bridged by a capacitor C29.
  • the first feedback circuit 30 includes a phase correction circuit comprising a resistor R65, a capacitor C31 and a resistor R66 connected between the base of transistor Ql and earth. R66 is bridged by a capacitor C32 and a variable capacitor C33.
  • the phase correction circuit is arranged to compensate for the phase change occurring in the main amplifying section 32, 34, 36. The phase change is only a few degrees.
  • Resistor R65 has a small resistance value compared to that of resistor R66 and capacitor C31 has a low impedance in the audio frequency range.
  • the signal appearing at the junction of capacitor C31 and resistor R66 is close in level to that of the input signal supplied to the base of transistor Ql and this signal is supplied to the non- inverting input of amplifier 60 on a line 63.
  • Capacitor C33 is adjusted so as to ensure that the two signals supplied to the two inputs of amplifier 60 are as closely in phase with each other as possible.
  • Resistor R61 is adjusted to ensure that their levels are as close as possible.
  • the output of amplifier 60 is connected through a resistor R67 to the inverting input of an operational amplifier 62, the output of which is connected to the inverting input through a resistor R68.
  • the amplifiers 60 and 62 together with their associated components function to subtract the output signal after attenuation to the level of the input signal from the input signal and to amplify the resulting signal.
  • This resulting signal which appears at the output of amplifier 62, is supplied through a resistor R69 and a line 64 to the base of transistor Q2.
  • this resulting signal is supplied as a negative feedback signal to the first stage 32.
  • the first feedback circuit 38 functions in a similar manner to the first feedback circuit of the amplifying circuit described with reference to Figure 1.
  • the distortion may be defined by the distortion factor.
  • the distortion factor is defined as one hundred times the square root of the ratio of the sum of the squares of the amplitudes of the distortion components in the output signal to the square of the amplitude of the fundamental component in the output signal.
  • the distortion factor lies in the range 0.1 to 0.5 percent. In the circuit described with reference to Figures 2 and 3, the distortion factor is below 0.001 percent.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)

Abstract

Un circuit d'amplificateur comprend un amplificateur principal (12) comportant une entrée (16) destinée à recevoir un signal d'entrée et une sortie (18) destinée à fournir un signal de sortie, un premier circuit de retour (14) et un second circuit de retour (R1, R2). Le premier circuit de retour (14) comprend un atténuateur (R3, R4) qui atténue le signal de sortie au niveau du signal d'entrée, un circuit de correction de phase (R3, R4) qui atténue le signal de sortie au niveau du signal d'entrée, un circuit de correction de phase (R8, C2, R9, C3) qui compense le signal d'entrée en fonction des changements de phase advenant dans l'amplificateur principal (12), et un amplificateur différentiel (22) qui soustrait le signal de sortie atténué du signal d'entrée à phase corrigée. La sortie de l'amplificateur différentiel (22) est amplifiée dans un amplificateur fonctionnel (23) et fournie à l'amplificateur principal (12) sous la forme d'un signal de retour négatif. Lors du fonctionnement, le premier circuit de retour (14) réduit grandement le niveau des composantes de distorsion dans le signal de sortie.
PCT/GB1993/000280 1992-02-13 1993-02-11 Circuit d'amplificateur WO1993016524A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP93904188A EP0626111A1 (fr) 1992-02-13 1993-02-11 Circuit d'amplificateur

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9203043A GB2261785B (en) 1992-02-13 1992-02-13 Amplifier circuit
GB9203043.6 1992-02-13

Publications (1)

Publication Number Publication Date
WO1993016524A1 true WO1993016524A1 (fr) 1993-08-19

Family

ID=10710321

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/000280 WO1993016524A1 (fr) 1992-02-13 1993-02-11 Circuit d'amplificateur

Country Status (3)

Country Link
EP (1) EP0626111A1 (fr)
GB (1) GB2261785B (fr)
WO (1) WO1993016524A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6489847B1 (en) 2000-01-28 2002-12-03 Telefonaktiebolaget Lm Ericsson Low distoration driving amplifier for integrated filters

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996002974A1 (fr) * 1994-07-13 1996-02-01 Bhc Consulting Pty. Ltd. Amelioration aux amplificateurs
AU696882B2 (en) * 1994-07-13 1998-09-24 Bhc Consulting Pty Ltd An improvement in amplifiers
GB2390946B (en) * 2002-07-10 2006-07-12 Aubrey Max Sandman Electronic amplifier circuit
GB2400995B (en) * 2003-03-28 2006-03-15 Gary Miller Linear amplifiers
DE102007011715B4 (de) * 2007-03-09 2012-08-30 Austriamicrosystems Ag Verstärkeranordnung zum Verstärken eines Signals

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4571553A (en) * 1983-12-14 1986-02-18 Nippon Gakki Seizo Kabushiki Kaisha Amplifier circuit with distortion cancellation function

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1368757A (en) * 1970-12-10 1974-10-02 Honeywell Inf Systems Electronic amplifiers
US4476442A (en) * 1981-04-03 1984-10-09 Nippon Gakki Seizo Kabushiki Kaisha Amplifier with distortion cancellation

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4571553A (en) * 1983-12-14 1986-02-18 Nippon Gakki Seizo Kabushiki Kaisha Amplifier circuit with distortion cancellation function

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
6TH EUROPEAN MICROWAVE CONFERENCE 1976 14-17 SEPTEMBER 1976 September 1976, ROME IT pages 410 - 414 S.A. PADOVANI ET AL 'LINEARIZATION OF L-BAND POWER TRANSISTOR AMPLIFIERS TO BE USED WITH A MULTICARRIER SIGNAL' *
ELECTRONICS INTERNATIONAL vol. 54, no. 8, 21 April 1981, NEW-YORK US page 185 A. COCCONI 'FEEDBACK REDUCES OFFSET IN WIDEBAND VIDEO AMPLIFIERS' *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6489847B1 (en) 2000-01-28 2002-12-03 Telefonaktiebolaget Lm Ericsson Low distoration driving amplifier for integrated filters

Also Published As

Publication number Publication date
EP0626111A1 (fr) 1994-11-30
GB2261785B (en) 1995-07-05
GB9203043D0 (en) 1992-03-25
GB2261785A (en) 1993-05-26

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