GB2331418A - Low voltage single-ended to differential amplifier with input transistors in common base and common emitter configurations - Google Patents

Low voltage single-ended to differential amplifier with input transistors in common base and common emitter configurations Download PDF

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Publication number
GB2331418A
GB2331418A GB9816128A GB9816128A GB2331418A GB 2331418 A GB2331418 A GB 2331418A GB 9816128 A GB9816128 A GB 9816128A GB 9816128 A GB9816128 A GB 9816128A GB 2331418 A GB2331418 A GB 2331418A
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GB
United Kingdom
Prior art keywords
transistors
amplifier
common
low
transistor
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.)
Granted
Application number
GB9816128A
Other versions
GB2331418A9 (en
GB2331418B (en
GB9816128D0 (en
Inventor
Jeffrey Michael Hond Smith
Colin Leslie Perry
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.)
Microchip Technology Caldicot Ltd
Original Assignee
Mitel Semiconductor Ltd
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
Publication of GB2331418A9 publication Critical patent/GB2331418A9/en
Application filed by Mitel Semiconductor Ltd filed Critical Mitel Semiconductor Ltd
Publication of GB9816128D0 publication Critical patent/GB9816128D0/en
Priority to DE69814309T priority Critical patent/DE69814309T2/en
Priority to EP98308484A priority patent/EP0917285B1/en
Priority to US09/185,837 priority patent/US6043710A/en
Priority to JP32340398A priority patent/JP3892160B2/en
Publication of GB2331418A publication Critical patent/GB2331418A/en
Application granted granted Critical
Publication of GB2331418B publication Critical patent/GB2331418B/en
Priority to JP2006282272A priority patent/JP4794410B2/en
Anticipated expiration legal-status Critical
Revoked legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/26—Push-pull amplifiers; Phase-splitters therefor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/14—Balanced arrangements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/14—Balanced arrangements
    • H03D7/1425—Balanced arrangements with transistors
    • H03D7/1433—Balanced arrangements with transistors using bipolar transistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
    • H03D7/14—Balanced arrangements
    • H03D7/1425—Balanced arrangements with transistors
    • H03D7/1458—Double balanced arrangements, i.e. where both input signals are differential
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0001—Circuit elements of demodulators
    • H03D2200/0033—Current mirrors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0041—Functional aspects of demodulators
    • H03D2200/0043—Bias and operating point
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D2200/00—Indexing scheme relating to details of demodulation or transference of modulation from one carrier to another covered by H03D
    • H03D2200/0041—Functional aspects of demodulators
    • H03D2200/0084—Lowering the supply voltage and saving power

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

Abstract

An amplifier comprises a common-base transistor 1 and a common-emitter transistor 2. The transistor 1 is arranged to receive an input signal applied to an input terminal 8 by an inductor 12 connected to its emitter. The transistor 2 is arranged to receive the input signal by a capacitor 13 connected to its base electrode. The transistors 1 and 2 are biased by a current mirror arrangement comprising a transistor 3 and a current source 16. Differential current output signals are provided on the collectors of the transistors 1 and 2. Fig 2 shows a two stage amplifier. Use in mixing and radio, particularty cellular, telephones is indicated.

Description

2331418 LOW-MOLIACTE AMPLIMES The present invention relates to low-voltage
amplifiers, and in particular although not exclusively to low-voltage amplifiers for use in radiotelephones.
The demands for large-signal handling capability in radiotelephones and in particular cellular phone circuits such as low-noise amplifiers and mixers are increasing, while the supply voltages on which they are required to operate are decreasing. For example, a few years ago battery voltages of 4.8 volts were common, whereas today cellular phone circuits may be required to operate from a 2.7 volt supply.
The lower supply voltage can make it difficult to design large-signal handling circuits around standard integrated circuit mixer configurations, such as Gilbert cells, which usually require a number of active devices to be stacked between the supply rails in order to be current efficient. These active devices may include, for example, the transistors of an input amplifier by means of which unbalanced or single- ended radio frequency received signals are amplified and phase-split to provide the balanced or differential current signals required to drive the transistors of a mixer cell.
EP-A-0584870 shows at Figure 2 thereof a transconductance amplifier comprising a common base transistor and a common emitter transistor arranged to receive a single-ended input signal and to provide differential current signals at their collector electrodes. However, this amplifier is not a low-voltage amplifier, and the present invention seeks to provide a low- voltage amplifier having improved or comparable transfer characteristics.
According to a first aspect of the present invention, there is provided a low-voltage amplifier for providing differential current outputs from a single-ended input comprising first and second transistors connected to receive signals from said input respectively in common-base and commonemitter configuration and means to forward bias the baseemitter junctions of said transistors, the differential outputs being derived from the collector electrodes of said first and second transistors.
According to a second aspect of the present invention there is provided a low-voltage amplifier for providing differential current outputs from a single-ended input comprising a first transistor connected to receive signals from said input in common- base configuration by an impedance, a second transistor connected to receive signals from said input in a common-emitter configuration by a capacitor, and means to forward bias the base-emitter junctions of said first and second transistors, the differential outputs being derived from the collector electrodes of said first and second transistors.
The capacitor acts as a dc block which therefore allows the base voltage of the common base connected transistor to be independent of the base voltage of the common-efflitter connected transistor. This allows more voltage headroom above the amplifier and can provide improved linearity and gain over prior art common-base/common emitter transistor amplifiers.
The means to forward bias the base-emitterj unctions of the first and second transistors may comprise a third transistor connected in a current-mirror configuration.
According to a third aspect of the present invention there is provided a low-voltage -3 amplifier for selectively providing differential current output signals from one or more of at least two amplifier stages in response to signals applied to a single- ended input common to the amplifier stages, each amplifier stage comprising a first transistor connected to receive signals from the input in a common-base configuration and a second transistor arranged to receive signals from the input in a common-emitter configuration, the emitter electrodes of at least two of said first transistors connected by a common first inductor to the input and the base electrodes of at least two of said second transistors connected by a common second inductor to a negative voltage supply line, the differential outputs of an amplifier stage being derived from the collector electrodes of the first and second transistors of that stage.
Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings of.
Figure 1 shows a low-voltage amplifier in accordance with the first and second aspects of the present invention; and Figure 2 shows a low-voltage amplifier in accordance with the first, second and third aspects of the present invention.
Referring to Figure 1, a low-voltage amplifier, comprising first, second and third transistors 1, 2 and 3, forms the input stage for a mixer stage comprising transistors 4, 5, 6 and 7. A radio frequency input signal is arranged to be applied between an input terTninal 8 and a common negative supply line or rail 9. A battery 10 providing, for example, 2.7 volts, may be connected between the line 9 and a positive supply line 11.
-4 The input terminal 8 is connected by way of a first inductor 12 to the emitter electrode of the first transistor 1 and by way of a first capacitor 13 to the base electrode of the second transistor 2, radiofrequency return paths to the line 9 being completed by way of a second capacitor 14 from the base electrode of the first transistor 1 and by way of a second inductor 15 from the emitter electrode of the second transistor 2.
Direct-current bias for the first and second transistors 1 and 2 is provided by biasing means comprising a current-mirror arrangement formed by a current source 16 and a third transistor 3, with first, second and third. biasing resistors 17, 18 and 19 connecting the collector circuit of the third transistor 3 to the base electrodes respectively of the first and second transistors 1 and 2 and the third transistor 3. The values of these resistors may be chosen to set the required values of current flow through the first and second transistors 1 and 2, compensating for their finite current gains. The second resistor 18 also provides a measure of radio frequency isolation of the bias arrangement from the radio frequency signals at the base electrode of the second transistor 2, while the first capacitor 13 provides a DC block to the bias at the base electrode of the second transistor 2. A direct current path to the line 9 for the emitter current of the first transistor 1 is provided by way of an inductor or rf choke 20 between the input terminal 8 and the line 9, the reactance of this choke 20 being accounted for in the design of the matching network normally provided at the input terminal 8.
It will be seen that for radio frequency signals the first transistor 1 is connected in commonbase configuration while the second transistor 2 is connected in common-emitter configuration, so that in response to radio frequency signals at the input terminal 8, differential current signals are provided from the collector electrodes of the first and second -5 transistors 1 and 2 to drive the mixer stage transistors 4 and 5 and 6 and 7 respectively.
These differential current signals are mixed in operation with local oscillator signals applied at terminals 21 and 22, and intermediate frequency output signals from the cross-coupled collector electrodes of the mixer transistors 4 to 7 are applied to a load circuit comprising load inductors 23 and 24 and a filter circuit comprising a resistor 25 and a capacitor 26.
Differential output voltage signals at intermediate frequency may be taken from first and second output terminals 27 and 28.
The first and second inductors 12 and 15 provide a measure of inductive degeneration, although this is not essential to the operation of the amplifier. For biasing purposes the inductors 12, 15 and 20 may be considered as very close to DC short circuit. The biasing means 3, 16, 14, 15, 12 enables the first and second transistors 1 and 2 to have their emitter electrodes very close to the potential of the line 9, thus maximising the proportion of the supply voltage which remains available to the rest of the circuit, that is, the mixer stage and the load circuit, where the largest voltage swings are to be expected.
The amplifier and mixer described above may be formed on an integrated circuit chip, indicated by the dashed outline 29, the choke 20 and the components 23 to 26 of the load circuit being provided externally, as shown, or on-chip.
Although only a preferred feature of the present invention, the inductors 12 and 15 can each tal(e up a large area on the integrated circ-it on which they are formed. The inventors have found that these inductors can be used also by one or more further amplifier circuits formed on the same integrated circuit. Figure 2 shows a low-voltage amplifier having two amplifying circuits.
Referring to Figure 2, a first amplifier stage comprises the amplifier of Figure 1, from which reference numerals have been re-used for like elements. The first amplifier stage is connected to a mixer core formed from transistors 4 to 7, as Mi Figure 1. A second amplifier stage is formed from fourth, fifth and sixth transistors 30, 31 and 32, each biased by their respective one of biasing resistors 34, 33 and 35. The base of the fourth transistor 30 is c;,nnected to the negative supply line 9 by a third capacitor 36 and the base of the fifth transistor 31 is connected to the input terminal 8 by a fourth capacitor 37. The emitter of the fourth transistor 30 is connected to the input terminal 8 by the first miductor 12, which it thereby shares with the first transistor 1. The fifth transistor 31 similarly shares the second inductor 15 with the second transistor 2.
The collector electrodes of the fourth and fifth transistors 30 and 31 form respective ones of differential current inputs to a second mixer core formed by transistors 38, 39,40 and 41. The second mixer core is arranged to receive local oscillator signals on local oscillator input terminals 42 and 43. A load circuit formed by load inductors 44 and 45 and a filter circuit formed by a capacitor 46 and a resistor 47 are connected between the output of the second mixer core and the positive supply line 11 and third and fourth output terminals 48 and 49 are provided in much the same way as the load and filter circuit arrangement of the first mixer core formed by the components 23 to 28.
The first amplifier stage is selected to handle signals applied to the input terminal 8 by switching on the current source 16 with the use of external control circuitry (not shown).
The second amplifier stage can similarly be selected for handling the signal applied to the input terminal 8 by selection of its current source 50, by the same or similar external control circuitry (not shown). Whichever of the first and second amplifier stages is selected, its -7performance will not be compromised by the connection of the first and second transistors 1 and 2 or the fourth and fifth transistors 30 and 31 as the case may be because of the high emitter impedance of these transistors.
It is contemplated that the Figure 2 low-voltage amplifier arrangement will be of particular use in applications where the use of a variable frequency local oscillator is impractical, expensive or otherwise undesirable. The Figure 2 arrangement can allow two, different, fixed frequency local oscillator signals to be mixed with a single input RF signal using the circuitry formed on single integrated circuit. It is possible even to select both the first and the second amplifier stages at the same time, providing output signals on the terminals 27 and 28 and the terminals 48 and 49 simultaneously. Such output signals would of course be derived from the same input signal, but would be dependent on the local oscillator signals applied to their respective local oscillator input terminals 21, 22 and 42, 43.
If only one of the first and second amplifier stages is to be selected at any one time, further component reuse could be obtained by the connection of the collector electrodes of the transistors 4 and 38 together and the connection of the collector electrodes of the transistors 7 and 41 together, a single load circuit and a single filter circuit then being needed to provide intermediate frequency output s--gnals from the selected one of the mixer cores.
With the Figure 2 arrangement, it is possible to provide easily the first amplifier stage with a different gain to that of the second amplifier stage. Although this could be achieved by the fabrication of the fourth and fifth transistors 30 and 31 with different properties to those of the first and second transistors 1 and 2, the first and second inductors 12 and 15 could be connected in the following way to achieve the same effect. If, for example, the first and second transistors 1 and 2 are connected to the outermost end of a respective five turn inductor 12 and 15 and the input terminal 8 and the negative supply line 9 are connected respectively to the innermost ends of the inductors 12 and 15, the second amplifier stage could be provided with a higher gain by connecting the fourth and fifth transistors 30 and 31 to the fourth or to the third turn of the inductors 12 and 15.
It will be appreciated by the skilled person that further amplifier stages, and further mixer cores and load circuits if necessary, can be connected to the input terminal 8 in the same way as the second amplifier stage. Each further amplifier stage would require its own voltage biasing means, preferably a current source connected in a current mirror configuration as in the first and second amplifier stages shown in Figure 2. These further amplifier stages could share the inductors 12 and 15, or could involve separate inductors.
CLATMS A low-voltage amplifier for providing differential current outputs from a singleended input comprising first and second transistors connected to receive signals from said input respectively in common-base and commonemitter configuration and means to forward bias the base-emitter junctions of said transistors, the differential outputs being derived from the collector electrodes of said first and second transistors.
2. A low-voltage amplifier for providing differential current outputs from a single- ended input comprising a first transistor connected to receive signals from said input in common-base configuration by an impedance, a second transistor connected to receive signals from said input in a common- emitter configuration by a capacitor, and means to forward bias the base- emitter junctions of said first and second transistors, the differential outputs being derived from the collector electrodes of said first and second transistors.

Claims (1)

  1. A low-voltage amplifier in accordance with Claim 2 in which the impedance
    comprises an inductor.
    4. A low-voltage amplifier in accordance with any preceding claim in which the emitter electrode of the second transistor is connected to ground potential by an inductor.
    5. A low-voltage amplifier in accordance with any preceding claim wherein the means -10to forward bias the base-emitter junctions of the first and second transistors comprises a third transistor connected in a current-mirror configuration.
    6. A low-voltage amplifier for selectively providing differential current output signals from one or more of at least two amplifier stages in response to signals applied to a single-ended input common to the amplifier stages, each amplifier stage comprising a first transistor connected to receive signals from tile input in a common-base configuration and a second transistor arranged to receive signals from the input in a common-emitter configuration, the emitter electrodes of at least two of said first transistors connected by a common first inductor to the input and the base electrodes of at least two of said second transistors connected by a common second inductor to a negative voltage supply line, the differential outputs of an amplifier stage being derived from the collector electrodes of the first and second transistors of that stage.
    7. A low-voltage amplifier in accordance with Claim 6 in which at least one of said second transistors is connected to receive the signals from the input by a capacitor.
    8. A low-voltage amplifier in accordance with Claim 6 or 7 further comprising biasing means associated with each amplifier stage, each biasing means selectable to forward bias the base emitter junctions of the first and second transistors of its associated amplifier stage.
    9. A low-voltage amplifier in accordance with Claim 8 in which the biasing means each comprise a third transistor connected in a current-mirror configuration.
    10. A mixer circuit arrangement including a low-voltage amplifier in accordance with any preceding claim.
    A radiotelephone including a mixer circuit arrangement in accordance with Claim 0.
    1 12. A low-voltage amplifier substantially as hereinbefore, described with reference to or as shown in Figure 1 or Figure 2 of the accompanying drawings.
GB9816128A 1997-11-14 1998-07-24 Low-voltage amplifiers Revoked GB2331418B (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DE69814309T DE69814309T2 (en) 1997-11-14 1998-10-16 Low Voltage Amplifier
EP98308484A EP0917285B1 (en) 1997-11-14 1998-10-16 Low-voltage amplifiers
US09/185,837 US6043710A (en) 1997-11-14 1998-11-04 Low-voltage amplifiers
JP32340398A JP3892160B2 (en) 1997-11-14 1998-11-13 Low voltage amplifier
JP2006282272A JP4794410B2 (en) 1997-11-14 2006-10-17 Low voltage amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB9724136.8A GB9724136D0 (en) 1997-11-14 1997-11-14 Low-voltage amplifier

Publications (4)

Publication Number Publication Date
GB2331418A9 GB2331418A9 (en)
GB9816128D0 GB9816128D0 (en) 1998-09-23
GB2331418A true GB2331418A (en) 1999-05-19
GB2331418B GB2331418B (en) 2003-01-15

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GBGB9724136.8A Ceased GB9724136D0 (en) 1997-11-14 1997-11-14 Low-voltage amplifier
GB9816128A Revoked GB2331418B (en) 1997-11-14 1998-07-24 Low-voltage amplifiers

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GBGB9724136.8A Ceased GB9724136D0 (en) 1997-11-14 1997-11-14 Low-voltage amplifier

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0584870A1 (en) * 1992-08-26 1994-03-02 Koninklijke Philips Electronics N.V. Transformer circuit, double-balanced mixer
WO1996023365A1 (en) * 1995-01-25 1996-08-01 Analog Devices Inc. Rf mixer with extended dynamic range

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5365192A (en) * 1993-08-11 1994-11-15 Trimble Navigation Limited AC-coupled single-ended or differential-input radio frequency amplifier integrated circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0584870A1 (en) * 1992-08-26 1994-03-02 Koninklijke Philips Electronics N.V. Transformer circuit, double-balanced mixer
WO1996023365A1 (en) * 1995-01-25 1996-08-01 Analog Devices Inc. Rf mixer with extended dynamic range

Also Published As

Publication number Publication date
GB2331418A9 (en)
GB2331418B (en) 2003-01-15
GB9816128D0 (en) 1998-09-23
GB9724136D0 (en) 1998-01-14

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773K Patent revoked under sect. 73(2)/1977

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