WO1996019042A1 - Comparateur differentiel avec seuil ajustable et hysteresis de poursuite - Google Patents

Comparateur differentiel avec seuil ajustable et hysteresis de poursuite Download PDF

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Publication number
WO1996019042A1
WO1996019042A1 PCT/US1994/014459 US9414459W WO9619042A1 WO 1996019042 A1 WO1996019042 A1 WO 1996019042A1 US 9414459 W US9414459 W US 9414459W WO 9619042 A1 WO9619042 A1 WO 9619042A1
Authority
WO
WIPO (PCT)
Prior art keywords
current
transistors
current switch
switch
coupled
Prior art date
Application number
PCT/US1994/014459
Other languages
English (en)
Inventor
Anthony R. Bonaccio
Original Assignee
International Business Machines Corporation
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 International Business Machines Corporation filed Critical International Business Machines Corporation
Priority to EP95910070A priority Critical patent/EP0797871A1/fr
Priority to PCT/US1994/014459 priority patent/WO1996019042A1/fr
Priority to KR1019970703445A priority patent/KR100239016B1/ko
Priority to JP8518713A priority patent/JPH10500549A/ja
Publication of WO1996019042A1 publication Critical patent/WO1996019042A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
    • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
    • H03K3/26—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback
    • H03K3/28—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback
    • H03K3/281—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator
    • H03K3/286—Generators characterised by the type of circuit or by the means used for producing pulses by the use, as active elements, of bipolar transistors with internal or external positive feedback using means other than a transformer for feedback using at least two transistors so coupled that the input of one is derived from the output of another, e.g. multivibrator bistable
    • H03K3/2893—Bistables with hysteresis, e.g. Schmitt trigger
    • H03K3/2897—Bistables with hysteresis, e.g. Schmitt trigger with an input circuit of differential configuration
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
    • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
    • H03K3/023—Generators characterised by the type of circuit or by the means used for producing pulses by the use of differential amplifiers or comparators, with internal or external positive feedback
    • H03K3/0233—Bistable circuits
    • H03K3/02337—Bistables with hysteresis, e.g. Schmitt trigger

Definitions

  • This invention generally relates to differential comparators and more particularly to a differential comparator that will make a decisive comparison of analog differential signals to an arbitrary threshold with an indication of whether the differential input is greater than or less than the threshold.
  • a high gain differential amplifier with no negative feedback can be used as a comparator to achieve this by connecting the positive input to the input signal and the negative input to the desired threshold.
  • the input signals are made differential for the purpose of rejecting noise that appears on the inputs with respect to a reference potential, e.g., ground.
  • a comparator the can directly handle a differential input signal is desirable.
  • the threshold is not fixed but rather changes as the average amplitude of the input signal changes. These changes occur because of temporal and positional variations in the read head, the magnetic medium, and etcetera. Differential signals are used in such a system for the reasons noted above. Hence a different comparator with an adjustable threshold is desirable.
  • the digital logic that is required to process the output of such comparators requires a firm signal at the comparator output. If the comparator output hangs in the middle of two logic levels or if it switches rapidly between the logic levels the digital logic cannot interpret the output. This problem is especially prevalent when the input signal is close to the threshold voltage of the comparator.
  • the present invention provides a differential comparator which is provided with an adjustable threshold and a hysteresis that tracks the threshold as it is adjusted.
  • the present invention is a programmable comparator circuit having a pair of differential inputs coupled through respective identical resistor networks, to turn on an active device in a first current switch. Turning on this device in the current switch permits the comparison of the differential of the inputs to a threshold voltage established by a selected value of current through a respective one of the resistor networks. This establishes a bias current through one of the transistors forming the first current switch, and through a second current switch for turning on the second switch and thus establishing a hysteresis current through one of the transistors forming the second current switch. By providing positive feed back means from the output of said first current switch control of the second current switch is assured.
  • Fig. 1 is a simple embodiment of the present invention in schematic form.
  • Fig. 2 is the preferred embodiment of the present invention in schematic form.
  • FIG. 1 there is shown a simple embodiment of the comparator circuit of the present invention in schematic form.
  • This schematic sets forth the comparator circuit 10 of the invention and includes a hysteresis switch 1 1 comprised of a pair of NPN, bipolar, emitter coupled transistors 12 and 13 whose emitters are coupled to ground 14 through a hysteresis current source 15.
  • the collectors of transistors 12 and 13 are respectively coupled, through respective hysteresis resistors 16 and 17, to respective differential inputs 18 and 19 and their bases are respectively coupled to the outputs 20 and 21 through respective diode pairs Dl, D2 and D3, D4.
  • the circuit 10 further includes a second emitter coupled switch formed of a pair of NPN, bipolar, emitter coupled, main amplifier transistors 22 and 23.
  • the 9042 PCIYUS94/14459 The 9042 PCIYUS94/14459
  • the output drive transistors 28 and 29 have their collectors coupled to the voltage source V DD and have their emitters respectively coupled to the respective outputs 20 and 21 and thence through the respective diode pairs Dl, D2 and D3, D4 to the bases of the respective switch transistors 12 and 13.
  • the described circuit operates as follows. It will be assumed that varying differential input voltage signals are respectively applied to the inputs 18 and 19. For purposes of this description, it will be assumed that initially the voltage of the signal applied to the input 18 is much higher than the voltage of the signal applied to the input 19.
  • the higher voltage applied to input 18 causes the amplifier transistor 22 to turn on to permit current to flow from the voltage source V DD through the current resistor 26, the transistor 22, and the current source 24 to ground 14.
  • transistor 22 turns on the voltage applied the base of the drive transistor 28 is lowered. Since transistor 28 operates as an emitter follower, the lowering of its base voltage also lowers the voltage at its emitter and at base of transistor 12 and transistor 12 is held off. Simultaneously, the transistor 23 is held off by the lower input voltage applied to its base from input 19.
  • transistor 23 Because transistor 23 is off the voltage applied to the base of the drive transistor 29 remains high, transistor 13 remains on and current flows from the input 19 through the hysteresis resistor 17, the transistor 13 and the hysteresis current source 15 to ground. It should be noted that the threshold current source 33 continues, under all circuit conditions to draw a constant current from the input 19 through both the hysteresis resistor 17 and the threshold resistor 31.
  • the hysteresis switch comprised of transistors 12 and 13, also enters its linear mode because of the feedback loops between the collectors of the hysteresis switch transistors 12 and 13 and the bases of the respective amplifier transistors 22 and 23 to which each of said collectors is respectively coupled.
  • These feedbacks between transistors 12 and 22 and between transistors 13 and 23 are positive and cause the entire network to switch when the feedback loops reach unity gain. This occurs approximately at the point at which the voltages applied to the bases of the transistors 22 and 23 become equal.
  • transistor 22 With transistor 22 now off the voltage applied to the base of the drive transistor 29 goes high turning on transistor 12 and current now flows from the input 18 through hysteresis resistor 16, transistor 12 and the hysteresis current source 15 to ground. It should be noted that the threshold current source 33 continues, under all circuit conditions to draw a constant current from the source 19 through both the hysteresis resistor 17 and the threshold resistor 31. If the input voltage VP, at input 19, now decreases with respect to the input voltage VN, at input 18, the circuit will eventually return to the initial state previously described. However the threshold voltage at which this occurs is different from that at which the circuit switched from the initial state.
  • the comparator has switch points at a voltage equal to the current flow I H through in the hysteresis current source 15 and the hysteresis resistor (Rrait) 16 i.e., I H R H above and below a threshold I T (R H + R ⁇ ) results in a hysteresis width of 2I H R H .
  • This means the hysteresis of the comparator can be set independently of the threshold voltage or can be set to track the threshold voltage by simply choosing the appropriate values of I ⁇ , I H , R ⁇ , and I
  • the comparator circuit of the invention includes a hysteresis current switch comprised of a pair of NPN, bipolar, emitter coupled transistors 112 and 113 whose emitters are coupled to ground 114 through a hysteresis current source 115.
  • the collectors of transistors 112 and 113 are respectively coupled through respective hysteresis resistors 116 and 117 to the emitters of a pair of NPN, bipolar, emitter follower transistors 140 and 141.
  • the collector of transistor 112 is connected to the emitter of emitter follower transistor 140 and the collector of auxiliary switch transistor 113 is coupled to the emitter of emitter follower transistor 141.
  • Respective differential inputs 1 18 and 119 are respectively coupled to the bases of these emitter follower transistors 140 and 141.
  • the bases of the switching transistors 112 and 1 13 are respectively coupled to the outputs 120 and 121 through respective diode pairs D7, D8, and D13, D14.
  • An auxiliary emitter coupled current switch is formed of NPN, bipolar transistors 142 and 143, whose bases are coupled in common with the bases of the switching transistors 112 and 113. This auxiliary current switch is also coupled between the emitter follower transistors 140 and 141 and ground 114.
  • the emitters of the auxiliary transistors 142 and 143 are coupled through a separate current source 115a to ground 114 and their collectors are cross-coupled to the respective emitters of the emitter follower transistors 140 and 141.
  • the collector of transistor 142 is connected to the emitter of emitter follower transistor 141 and the collector of auxiliary switch transistor 143 is coupled to the emitter of emitter follower transistor 140.
  • the circuit shown in Fig. 2 further includes a pair of NPN, bipolar, emitter coupled, main amplifier transistors 122 and 123.
  • the emitters of these main amplifier transistors 122 and 123 are coupled to ground 114 through a bias current source 124.
  • the collectors of these amplifier transistors 122 and 123 are respectively coupled to a supply voltage V DD through respective current resistors 126 and 127 and to the bases of respective output drive NPN, bipolar, transistors 128 and 129.
  • the bases of the main amplifier transistors 122 and 123 are respectively connected through respective threshold resistors 130 and 131 to the collectors of the switching transistors 112 and 1 13.
  • the base of amplifier transistor 123 is further coupled to ground 114 through a threshold current source 133.
  • the output drive transistors 128 and 129 have their collectors coupled to the voltage source V DD and have their emitters respectively coupled to the respective outputs 120 and 121 and thence through the respective diode pairs D7, D8 and D13, D14 to the bases of the respective switch transistors 112 and 1 13.
  • the addition of the emitter follower transistors 140 and 141 and the auxiliary current switch formed of transistors 142 and 143 significantly improve the operation of the comparator circuit of the present invention. By buffering the input voltages V P and V N with the emitter follower transistors 140 and 141, the effective load on the circuit driving these points is reduced.
  • the currents through the emitter follower transistors 140 and 141 can be made to be constant under all operating conditions by selectively setting the bias current levels passing through the second and third current switches i.e., the current switches respectively formed of transistors 124 and 133 and transistors 142 and 143.
  • the extra hysteresis current I H through the current source 115a is steered by the emitter follower transistor that is driving the main amplifier transistor that is on. This current is selected to assure that when all bias and base currents flowing in the circuit are accounted for, the total current in follower transistors 140 and 141 will be precisely equal.
  • the threshold voltage was 80% of the voltage difference between the external threshold voltage and the reference voltage and the actual width of the hysteresis was nominally 20% of the threshold voltage.
  • FETs field effect transistors
  • MOSFETSs field effect transistors
  • SUBSTITUTE SHEETS 26 that compares a differential input to a predetermined threshold voltage that can be adjusted by changing the voltage on of the differential inputs to the circuit.
  • the comparator of the invention further provides a hysteresis that tracks the threshold by a factor that is less than 1.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manipulation Of Pulses (AREA)

Abstract

Circuit comparateur programmable perfectionné comprenant une paire d'entrées différentielles (VN, VP), qui va enclencher un premier commutateur de courant (22, 23) par l'intermédiaire de réseaux de résistances identiques respectifs (16, 30, 17, 31) pour permettre d'effectuer la comparaison du différentiel des entrées avec une tension de seuil. La tension de seuil est établie par la tension qui est générée lorsque l'on fait passer un courant donné par un desdits réseaux de résistance, de sorte qu'un courant de polarisation traversant un des transistors constituant le premier commutateur de courant et traversant un deuxième commutateur de courant (12, 13), établisse un courant d'hystérésis à travers un des transistors constituant le deuxième commutateur de courant. Un dispositif de rétroaction positive (28, 29, D1-D4) couplé à la sortie du premier commutateur de courant (22, 23) commande le deuxième commutateur de courant (12, 13).
PCT/US1994/014459 1994-12-16 1994-12-16 Comparateur differentiel avec seuil ajustable et hysteresis de poursuite WO1996019042A1 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP95910070A EP0797871A1 (fr) 1994-12-16 1994-12-16 Comparateur differentiel avec seuil ajustable et hysteresis de poursuite
PCT/US1994/014459 WO1996019042A1 (fr) 1994-12-16 1994-12-16 Comparateur differentiel avec seuil ajustable et hysteresis de poursuite
KR1019970703445A KR100239016B1 (ko) 1994-12-16 1994-12-16 조절가능한 문턱값과 트래킹 히스테리시스를 갖는 차동 비교기
JP8518713A JPH10500549A (ja) 1994-12-16 1994-12-16 調整可能な閾値及びトラッキング・ヒステリシスを有する差動コンパレータ

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1994/014459 WO1996019042A1 (fr) 1994-12-16 1994-12-16 Comparateur differentiel avec seuil ajustable et hysteresis de poursuite

Publications (1)

Publication Number Publication Date
WO1996019042A1 true WO1996019042A1 (fr) 1996-06-20

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1994/014459 WO1996019042A1 (fr) 1994-12-16 1994-12-16 Comparateur differentiel avec seuil ajustable et hysteresis de poursuite

Country Status (4)

Country Link
EP (1) EP0797871A1 (fr)
JP (1) JPH10500549A (fr)
KR (1) KR100239016B1 (fr)
WO (1) WO1996019042A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0955728A2 (fr) * 1998-05-04 1999-11-10 Nortel Networks Corporation Procédé et appareil pour exécuter la détection d'impulsions de données
WO2000045507A1 (fr) * 1999-01-28 2000-08-03 Nortel Networks Limited Recepteur d'impulsions de donnees

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20240033762A (ko) 2022-09-05 2024-03-13 김남국 밀링머신의 밀링커터

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3757137A (en) * 1969-12-18 1973-09-04 Rca Corp Low voltage reference circuit
US5039888A (en) * 1989-11-14 1991-08-13 Harris Corporation Method and circuit arrangement for providing programmable hysteresis to a differential comparator
EP0452967A2 (fr) * 1990-04-21 1991-10-23 Kabushiki Kaisha Toshiba Comparateur d'hystérésie

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3757137A (en) * 1969-12-18 1973-09-04 Rca Corp Low voltage reference circuit
US5039888A (en) * 1989-11-14 1991-08-13 Harris Corporation Method and circuit arrangement for providing programmable hysteresis to a differential comparator
EP0452967A2 (fr) * 1990-04-21 1991-10-23 Kabushiki Kaisha Toshiba Comparateur d'hystérésie

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
GILES ET AL: "Un nouveau comparateur très rapide: le AM 685", ELECTRICITE ELECTRONIQUE MODERNE, no. 285, January 1976 (1976-01-01), PARIS FR, pages 29 - 33 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0955728A2 (fr) * 1998-05-04 1999-11-10 Nortel Networks Corporation Procédé et appareil pour exécuter la détection d'impulsions de données
EP0955728A3 (fr) * 1998-05-04 2001-11-28 Nortel Networks Limited Procédé et appareil pour exécuter la détection d'impulsions de données
WO2000045507A1 (fr) * 1999-01-28 2000-08-03 Nortel Networks Limited Recepteur d'impulsions de donnees
US6529564B1 (en) 1999-01-28 2003-03-04 Nortel Networks Limited Data pulse receiver

Also Published As

Publication number Publication date
KR100239016B1 (ko) 2000-01-15
JPH10500549A (ja) 1998-01-13
EP0797871A1 (fr) 1997-10-01
KR980700730A (ko) 1998-03-30

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