EP0916183A1 - Amplificateur d'adaptation d'impedance ameliore - Google Patents

Amplificateur d'adaptation d'impedance ameliore

Info

Publication number
EP0916183A1
EP0916183A1 EP98929147A EP98929147A EP0916183A1 EP 0916183 A1 EP0916183 A1 EP 0916183A1 EP 98929147 A EP98929147 A EP 98929147A EP 98929147 A EP98929147 A EP 98929147A EP 0916183 A1 EP0916183 A1 EP 0916183A1
Authority
EP
European Patent Office
Prior art keywords
amplifier
transimpedance amplifier
addition
improved
improved transimpedance
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP98929147A
Other languages
German (de)
English (en)
Inventor
Valentino Corso
Ezio Maria Bastida
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fundacao Cpqd - Centro De Pesquisa E Desenvolvimen
Original Assignee
BRASILIA TELECOM
TELECOMUNICACOES BRASILEIRAS S/A-TELEBRAS
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 BRASILIA TELECOM, TELECOMUNICACOES BRASILEIRAS S/A-TELEBRAS filed Critical BRASILIA TELECOM
Publication of EP0916183A1 publication Critical patent/EP0916183A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3084—Automatic control in amplifiers having semiconductor devices in receivers or transmitters for electromagnetic waves other than radiowaves, e.g. lightwaves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/42—Amplifiers with two or more amplifying elements having their DC paths in series with the load, the control electrode of each element being excited by at least part of the input signal, e.g. so-called totem-pole amplifiers
    • H03F3/423—Amplifiers with two or more amplifying elements having their DC paths in series with the load, the control electrode of each element being excited by at least part of the input signal, e.g. so-called totem-pole amplifiers with MOSFET's
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G1/00—Details of arrangements for controlling amplification
    • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
    • H03G1/0017—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal the device being at least one of the amplifying solid-state elements
    • H03G1/0023—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal the device being at least one of the amplifying solid-state elements in emitter-coupled or cascode amplifiers

Definitions

  • the present invention relates to transimpedance amplifiers, and more specifically to monolithic amplifiers to be manufactured in large quantities for use in wide-band low-cost optical front-ends.
  • the optical signal is usually transmitted through optical fiber, whose receiver - or repeater - end is coupled to a photodiode that converts the optical signal into an electrical current signal.
  • Transimpedance amplifiers are low noise devices that convert this electric current into a voltage signal with a magnitude adequate for subsequent electronic processing.
  • Such amplifiers are certainly the most important elements of optical receivers, since they practically determine basic receiver - or repeater - features, such as bandwidth, sensitivity, dynamic range and bit error rate. The lower the amplifier noise the better the receiver sensitivity will be, and, therefore, its ability to be used for longer transmitter to receiver spacings for a given transmitted optical power level.
  • the current is converted into voltage by means of a feedback resistor R F bridging input and output of an inverting amplifier.
  • R F feedback resistor
  • the value of this resistor must be carefully chosen since a higher resistance increases the gain of the amplifier while decreasing the equivalent noise current .
  • the amplifier bandwidth as well as its dynamic range are inversely proportional to the value of R F .
  • said bandwidth decreases in accordance with the parasitic capacitance of the photodiode as well as with the number of stages constituting the inverting amplifier.
  • low frequency circuits normally include several stages, while very large bandwidth circuits use a configuration in which the amplification is performed by a single transistor (here called, for brevity, single transistor inverter).
  • the single transistor inverter should use a low feedback resistance, therefore preserving the bandwidth. However, as noted before, this degrades the achievable noise performance.
  • single inductor peaking such as shown in Fig. 1, or double inductor peaking such as shown in Fig. 2, were introduced in single transistor inverters.
  • the feedback resistors that provide conversion of current into voltage are referred to as 19 in
  • Amplifiers such as those shown in figures 1, 2 and 3 are used in large numbers in optical communication systems, therefore the utilization of said devices assembled from discrete components would bring the systems' cost to prohibitive levels.
  • these circuits are realized in monolithic form - producing high volume low cost devices - the resulting amplifiers show increased dependence on the manufacturing process drift. In some cases, these circuits show a tendency to oscillate, lowering the yield of the manufacturing process, since the circuits so affected have to be discarded. This can be seen in the graph in Fig. 5, where curve 81 illustrates the frequency response when the component values are in the middle of the tolerance range, and curve 82 shows the behavior of the same circuit when a particular process fluctuation brought some component values to the limit of the tolerance range.
  • a second objective of the invention is to make the performance of these amplifiers substantially independent of fluctuations that occur during manufacturing or to provide practical low-cost ways to compensate for said fluctuations.
  • Another objective is to provide circuits capable of operating with no substantial bandwidth reduction, even when low-cost photodiodes are used. Such diodes usually have a much higher capacitance than their more expensive counterparts.
  • the transimpedance amplifier gain control is provided by the addition or subtraction of a controlled D.C. current to the first transistor cascode inverter stage so as to adjust its transconductance.
  • said control current is provided by a control resistor which is connected between the inverter transistor and a fixed or adjustable voltage source.
  • said control current is supplied by an accessory current supply circuit that adds or subtracts a controlled amount of D.C. current to said first inverter transistor.
  • Figure 1 shows a single device inverter transimpedance amplifier with single inductor peaking, according to the previous known art.
  • Figure 2 shows a single device inverter transimpedance amplifier with double inductor peaking, according to the previous state of the art.
  • Figure 3 shows a cascode transimpedance amplifier with double inductor peaking, from which single inductor circuits can be derived by short circuiting one of its inductors.
  • Figure 4 shows a first preferred embodiment of the invention, comprising a cascode transimpedance amplifier with double inductor peaking and a gain control resistor.
  • Figure 5 shows a typical effect of the process fluctuation on the Fig. 3 amplifier bandwidth, considering the total input capacitance of 0,5 pF (photodiode + stray).
  • Figure 6 shows the peaking control and stabilizing action as a function of the voltage applied to the control resistor for a Fig. 4 circuit. Double inductor peaking is used and a total input capacitance (photodiode + stray) of 0,5 pF is taken into account.
  • Figure 7 shows a second preferred embodiment of the invention, comprising a cascode type transimpedance amplifier with double inductor peaking, positive current feedback a gain control resistor.
  • Single inductor circuits, in accordance with the invention, are obtained by short circuiting one of the inductors.
  • Figure 8 shows the experimental response curves for the Fig. 7 circuit as a function of the total input capacitance (photodiode + stray), between 0 and 1.2pF in 0.2pF steps, when no control voltage is applied.
  • Figure 9 shows the frequency response curves for the same circuit, under similar conditions of input , when the control voltage is -4N.
  • Figure 10 shows the schematic of the first embodiment of the invention, when adapted for operation with a single power supply.
  • Figure 11 shows the schematic of the second embodiment of the invention, when adapted for operation with a single power supply.
  • the first transistor 65 performs the inverting amplifying action
  • the second transistor 66 functions as a grounded gate non-inverting amplifier
  • third transistor 67 works as the active load of the cascode stage.
  • Transistor 69 is a current source used for obtaining the DC voltage that biases the gate of 66
  • transistors 73 and 74 form the output buffer amplifier of the source follower type.
  • Inductor 64 resonates in series with the input capacitance of transistor 65, so that voltage gain increases with signal frequency.
  • Inductor 68 has a similar effect, increasing the load of the cascode stage at high frequencies, reducing the noise fluctuations of the current that circulates in the amplifying devices. By shorting either inductor 64 or 68, a single inductor configuration is obtained.
  • Block 100 is a series connected cascade of diodes, performing a DC level shifting of the bias voltage applied to the gate of transistor 66.
  • Gain control resistor 71 has a high enough value to prevent a substantial degrading of the amplifier's noise performance as well as its voltage gain.
  • This resistor can be connected either to an external voltage source or to the positive or negative supplies or to ground. The value of this voltage is a function of measurements performed in specific locations of the semiconductor wafer during manufacture, prior to the dicing into individual chips.
  • an external resistor may be connected in series with resistor 71. On-chip resistor trimming methods can also be employed.
  • a resistor 71 instead of a resistor 71, one may make use of any circuit capable of adding or subtracting in a controlled manner DC current to or from the input transistor, provided that said circuit does not substantially degrade the amplifier gain, bandwidth, dynamic range or noise performances.
  • Computer simulations of the Fig. 4 circuit performance were conducted, showing a transimpedance bandwidth greater than 3,5 GHz, with extremely low equivalent input noise current densities ( ⁇ 4pA/Hz ,/2 ), using standard low-cost 0.5 ⁇ m gate gallium arsenide MESFET's.. These results enable the circuit for use in 5Gbits/s links.
  • the maximum bit rate obtained with a cascode configuration using this technology was about one-half (2.5Gbit/s) and the equivalent noise input current densities were higher than 5pA/Hz 1/2 .
  • the circuit configuration shown in Fig. 4 resultsin a very high overall device yield per wafer.
  • Figure 5 shows the effect of the process fluctuations on the circuit performance, when lead 72 is unconnected, meaning that resistor 71 is out of the circuit. Under such conditions, the circuit of Fig. 4 becomes identical to the one in Fig. 3.
  • the frequency response curves of the graph in Fig. 5 were calculated for a total input capacitance of 0.5pF with the PSPICE program, by using data from the Triquint foundry for 0.5 ⁇ m GaAs FET's.
  • Curve 81 shows the performance with nominal process conditions, while curve 82 results when a particular process fluctuation (LLLOLO) occurs. This curve shows a large undesired peaking of the transimpedance function which makes the amplifier unsuitable for use in optical receivers, mainly due to the fact that the circuit is working very near to oscillation conditions.
  • FIG. 7 Another preferred embodiment of the invention is shown in Fig. 7, in which positive current feedback is applied from transistor 124 source to the drain of transistor 115. This adds to the total current flow through the latter, therefore increasing its transconductance. Similarly to the previous circuit, in the present configuration transistor 115 drain current can be either added or subtracted through resistor 121, thereby providing a gain adjustment in this stage.
  • a circuit having the Fig. 7 configuration was designed for use with PIN photodiodes for 2,5Gbits/s links and fabricated at the Marconi foundry. Tests conducted with this circuit produced the set of curves of Fig. 8, in which curve 131 corresponds to zero total input parasitic capacitance (photodiode + stray), and the following ones, to 0.2pF capacitance increments, with no control voltage applied. It can be seen that the circuit performs well even with parasitic capacitances of the order of lpF (see curve 136). However, with low values of Ctot (sum of the photodiode and the stray capacitances), the curves show undesired high-frequency peaking (curves 132 and 135).
  • the transconductance bandpass shows an increase of 0.3GHz on the high frequency end.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Amplifiers (AREA)

Abstract

L'invention concerne un amplificateur d'adaptation d'impédance amélioré sous forme de circuit intégré monobloc, comprenant un étage amplificateur inverseur cascode présentant au moins une bobine d'inductance de relèvement (64, 68, 114, 118, 152, 157, 172, 177) suivie d'un ou plusieurs étages amplificateurs. Le gain de l'amplificateur d'adaptation d'impédance est régulé par le réglage du courant continu circulant à travers le premier étage inverseur cascode du transistor (65, 115, 153, 173) de façon à réguler sa transconductance. Ledit réglage consiste à augmenter ou diminuer le courant au point de connexion des premier et second transistors dans l'étage amplificateur inverseur cascode, soit au moyen d'une résistance reliée entre ladite connexion et une source de tension prédéterminée positive, négative ou égale à zéro, soit au moyen d'un circuit d'alimentation en courant accessoire qui augmente ou diminue une quantité de courant continu régulée.
EP98929147A 1997-05-30 1998-06-01 Amplificateur d'adaptation d'impedance ameliore Withdrawn EP0916183A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
BR9703233 1997-05-30
BR9703233A BR9703233A (pt) 1997-05-30 1997-05-30 Aperfeiçoamento introduzido em amplificador de transimpedancia
PCT/BR1998/000030 WO1998054833A1 (fr) 1997-05-30 1998-06-01 Amplificateur d'adaptation d'impedance ameliore

Publications (1)

Publication Number Publication Date
EP0916183A1 true EP0916183A1 (fr) 1999-05-19

Family

ID=4067550

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98929147A Withdrawn EP0916183A1 (fr) 1997-05-30 1998-06-01 Amplificateur d'adaptation d'impedance ameliore

Country Status (3)

Country Link
EP (1) EP0916183A1 (fr)
BR (1) BR9703233A (fr)
WO (1) WO1998054833A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002043875A (ja) * 2000-07-24 2002-02-08 Nec Corp 可変利得増幅器及びそれを備えた電子機器
DE102004009684B4 (de) * 2004-02-27 2014-12-24 Infineon Technologies Ag Transimpedanzverstärkeranordnung für hohe Schaltfrequenzen
EP1993201A1 (fr) * 2007-05-18 2008-11-19 Interuniversitair Microelektronica Centrum Vzw Conception des amplifications faible bruit multibande commutable

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8728853D0 (en) * 1987-12-10 1988-01-27 Bt & D Technologies Ltd Transimpedance pre-amplifier & receiver including pre-amplifier
JPH05304422A (ja) * 1992-04-24 1993-11-16 Sumitomo Electric Ind Ltd 光通信用前置増幅器
US5572074A (en) * 1995-06-06 1996-11-05 Rockwell International Corporation Compact photosensor circuit having automatic intensity range control

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9854833A1 *

Also Published As

Publication number Publication date
WO1998054833A1 (fr) 1998-12-03
BR9703233A (pt) 1998-12-29

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