CN1142634C - Gain-variable amplifier for transmitting end - Google Patents
Gain-variable amplifier for transmitting end Download PDFInfo
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- CN1142634C CN1142634C CNB021254494A CN02125449A CN1142634C CN 1142634 C CN1142634 C CN 1142634C CN B021254494 A CNB021254494 A CN B021254494A CN 02125449 A CN02125449 A CN 02125449A CN 1142634 C CN1142634 C CN 1142634C
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- variable gain
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Abstract
The present invention belongs to the technical field of analog signal processing and communication, and relates to a variable gain amplifier used for a transmitting end, which comprises a plurality of same variable gain basic units in cascade connection and a control voltage generator, wherein the output end of each of the variable gain basic units is connected with the control voltage generator; the variable gain basic units are composed of a plurality of source followers with variable gain in direct cascade connection, and the source follower in the last stage comprises MOS tubes M1, M2, an MOS tube Mc_1 as a variable resistor and resistors R1 and R2 for biasing; each of the source followers in previous stages is formed by adding a pair of bias resistors and an MOS tube as a variable resistor on the basis of the source follower in the next stage. The present invention can be manufactured in a CMOS-process, and the present invention has the advantages of large range of control voltage, linear gain on dB, large dynamic range of the gain, small chip area, low voltage and low power consumption.
Description
Technical field
The invention belongs to analog and communication technical field, particularly be suitable for the variable gain amplifier design of wireless transceiver and audio frequency/video analog signal treatment circuit.
Background technology
Variable gain amplifier is widely used in telecommunication circuit and the audio frequency/video analog signal treatment circuit, generally need variable gain amplifier have gain on dB with linear, the big output gain scope of control voltage, big input dynamic range, low noise, low-voltage and low-power consumption.Whether the performance quality of variable gain amplifier directly has influence on the performance of system.And many and high to index, the requirement of variable gain amplifier, make that the good variable gain amplifier of design performance is the comparison difficulty.
The variable gain amplifier of use in transmitter has different places with the variable gain amplifier of use in receiver in the requirement of gain: the gain that the former needs is little, and maximum gain is 0dB usually, and the gain that the latter generally need be high.On other index, the two is consistent.
Make that the gain ranging of variable gain amplifier is big, general consideration is that several identical variable gain elementary cells are cascaded up, the type of attachment of a typical variable gain amplifier is as shown in Figure 1: the connection between the variable gain elementary cell can directly be coupled also can pass through capacitive coupling, the input of the control voltage of variable gain elementary cell is to be provided and distributed by the control voltage generator, the control voltage of each variable gain elementary cell can be the same or different, and decides according to the circuit structure that the variable gain elementary cell is concrete.For the variable gain elementary cell, if its variable gain scope is little, just need a lot of such elementary cell cascades, will cause the bandwidth of whole variable gain amplifier to reduce like this, and increasing DC maladjustment can appear, also can cause the shared chip area of circuit to increase.So the designer generally is absorbed in the realization of the good variable gain elementary cell of performance.
Linear on dB in order to realize gain, traditional variable gain amplifier often adopts twin-stage type technology, utilize the special nature of twin-stage transistor npn npn: collector current and base voltage have exponential relationship, realize that gain has index character with control voltage, just linear with control voltage on dB.And in CMOS technology, metal-oxide-semiconductor does not have such index character, so can only approach index character with approximate method, just dB goes up linear character.
Be no more than 0dB since be used for the variable gain amplifier maximum gain of transmitting terminal,, and use the metal-oxide-semiconductor that is in linear zone to realize the change that gains as variable resistor so traditional method uses the source class follower to realize.The circuit of the variable gain elementary cell that a kind of typical C MOS technology realizes as shown in Figure 2, by three metal-oxide-semiconductor M1, M2 and Mc_1, two current source Id1, Id2 form, its annexation is: input signal Vin+, Vin-receive respectively on the grid level of metal-oxide-semiconductor M1 and metal-oxide-semiconductor M2, and the leakage level of metal-oxide-semiconductor M1 and M2 is connected on the power supply Vdd; The source class of metal-oxide-semiconductor M1 is connected to be provided on the current source of the bias current Id1, the source class of metal-oxide-semiconductor M2 is connected to be provided on the current source of the bias current Id2, simultaneously, the source class of metal-oxide-semiconductor M1 and M2 is connected respectively to a source class and a leakage level that is in the metal-oxide-semiconductor Mc_1 of linear zone.The leakage level of metal-oxide-semiconductor M1 and M2 is an output signal end.Control voltage Vc receives on the grid level of metal-oxide-semiconductor Mc_1.Change the equivalent resistance of metal-oxide-semiconductor Mc_1 like this by the grid step voltage that changes metal-oxide-semiconductor, realize the change of gain.
Above-mentioned this circuit has the following disadvantages:
The first, gain is not linear relationship on dB, and is only just approximate on a very little segment limit;
The second, the input control voltage scope is very little, generally has only 1V;
Three, gain dynamic range is little, and effectively gain dynamic range has only about 15dB;
Four, direct several similar variable gain elementary cells of cascade, because every through one-level, its output point
Will the descend threshold voltage vt h of a metal-oxide-semiconductor of direct voltage.Like this, cascade just be merely able to by every
Straight electric capacity carries out AC coupled, if realize the gain variation range of 70dB, just needs 5 grades at least
Such variable gain elementary cell will have 8 capacitances at least, takies a large amount of chip areas.
Summary of the invention
The objective of the invention is for overcoming the weak point of prior art, a kind of variable gain amplifier that is used for receiving terminal is proposed, can use the CMOS prepared, have that the control voltage range is big, gain linear, big gain dynamic range, chip area on dB is little, low-voltage, advantage of low power consumption.
A kind of variable gain amplifier that is used for transmitting terminal that the present invention proposes, variable gain elementary cell and control voltage generator two parts of comprising a plurality of identical cascades, the output of said each variable gain elementary cell links to each other with the control voltage generator, it is characterized in that, said variable gain elementary cell is formed by the direct cascade of source class follower of a plurality of variable gains, wherein the source class follower of afterbody comprises: metal-oxide-semiconductor M1, M2, and as variable-resistance metal-oxide-semiconductor Mc_1, as the resistance R 1 and the R2 of biasing; Its annexation is: the output signal of previous stage is input on the grid level of M1, and another output signal of previous stage is input on the grid level of M2, and the leakage level of M1, M2 is all received on the power supply Vdd; The source class of M1 and M2 is connected the source class of Mc_1 pipe respectively and leaks level, connects respectively simultaneously on the end of R1 and R2; The other end of R1 and R2 is connected to ground; The grid level of Mc_1 is the input of control voltage input signal Vc2, and the source class end of M1 and M2 is the output of this grade signal; The formation of inferior final stage source class follower is to have increased a pair of biasing resistor R3, R4 on the basis of one-level source class follower configuration in the end and as variable-resistance metal-oxide-semiconductor Mc_2, wherein, R3 connects the end of R1, the other end ground connection of R3, R4 connects the end of R2, the other end ground connection of R4, the source of Mc_2, drain electrode connect the end of R1 and R2 respectively, also are the ends of R3 and R4 simultaneously; And the grid level of the grid level of Mc_2 and Mc_1 to link together be the input of control voltage input signal Vc1; By that analogy, the formation of previous stage source class follower all is to have increased a pair of biasing resistor and as variable-resistance metal-oxide-semiconductor on the basis of one-level source class follower configuration thereafter.
The design of CMOS variable gain amplifier of the present invention is compared with the traditional design scheme has following tangible advantage:
1) this variable gain amplifier have gain with control voltage on the scope of input control voltage, on dB, be approximate linear;
2) it is big to have increased the control input voltage range, can reach 0～Vdd;
3) Zeng Yi dynamic range is big, and the actual gain dynamic range can reach 70dB;
4) dynamic range of input signal is big, can reach 70dB;
5) the capacitance number is few, and general needs 2 electric capacity just passable;
6) the frequency height of suitable work;
7) low in energy consumption.
Description of drawings
Fig. 1 is the structured flowchart of typical variable gain amplifier.
Fig. 2 is the topological structure schematic diagram of the variable gain elementary cell of traditional CMOS variable gain amplifier.
Fig. 3 is the block diagram of CMOS variable gain amplifier of the present invention.
Fig. 4 is the topological structure schematic diagram of the variable gain elementary cell of CMOS variable gain amplifier of the present invention.
Embodiment
A kind of CMOS variable gain amplifier that is used for transmitting terminal that the present invention proposes reaches embodiment in conjunction with the accompanying drawings and is described in detail as follows:
The CMOS variable gain amplifier embodiment circuit structure that the present invention proposes as shown in Figure 3, comprise variable gain elementary cell and control voltage generator two parts of a plurality of identical cascades, the output of said each variable gain elementary cell links to each other with the control voltage generator.This is typical ways of connecting, and gain control range can reach 70dB, and bigger if desired gain control range just re-uses AC coupled and connects.External input signal is radiofrequency signal Vin+ and Vin-, direct-current control voltage signal Vc and the high level voltage power supply signal Vdd of difference input.Control voltage generator among the figure produces 3 control voltage Vc0, Vc1 and Vc2, is input to the variable gain elementary cell and goes.The particular circuit configurations and the annexation of each several part are described in detail as follows:
Variable gain elementary cell example structure of the present invention is that the direct cascade of source class follower by three variable gain forms as shown in Figure 4, and three empty frames are represented the source class follower of these 3 variable gains respectively among the figure.
The source class follower of afterbody comprises: metal-oxide-semiconductor M1, M2, and as variable-resistance metal-oxide-semiconductor Mc_1, as the resistance R 1 and the R2 of biasing.Its annexation is: the output signal of previous stage is input on the grid level of M1, and another output signal of previous stage is input on the grid level of M2, and the leakage level of M1, M2 is all received on the power supply Vdd.The source class of M1 and M2 is connected the source class of Mc_1 pipe respectively and leaks level, connects respectively simultaneously on the end of R1 and R2; The other end of R1 and R2 is connected to ground.The grid level of Mc_1 is the input of control voltage input signal Vc2.The output signal end of this grade is the source class end of M1 and M2.
The formation of inferior final stage source class follower is to have increased a pair of biasing resistor R3, R4 on the basis of one-level source class follower configuration in the end and as variable-resistance metal-oxide-semiconductor Me_2.Wherein, R3 connects the end of R1, the other end ground connection of R3, and R4 connects the end of R2, the other end ground connection of R4, the source of Mc_2, drain electrode connect the end of R1 and R2 respectively, also are the ends of R3 and R4 simultaneously.And the grid level of the grid level of Mc_2 and Me_1 to link together be the input of control voltage input signal Ve1.
The formation of first order source class follower is not only than on the basis of inferior final stage source class follower configuration but also increased a pair of biasing resistor R5, R6 and as variable-resistance metal-oxide-semiconductor Mc_3.R5 connects the end of R3, the other end ground connection of R5, and R6 connects the end of R4, the other end ground connection of R6, the source of Mc_3, drain electrode connect the end of R3 and R4 respectively, also are the ends of R5 and R6 simultaneously.And the grid level of the grid level of the grid level of Mc_3, Mc_2 and Mc_1 to link together be the input of control voltage input signal Vc0.
The substrate ground connection of all metal-oxide-semiconductors in the variable gain basic element circuit.
The operation principle of the circuit of present embodiment is:
With reference to the accompanying drawings 3, the control voltage of each variable gain elementary cell is all the same, is a group of control voltage signal Vc0, Vc1 and the Vc2 that is produced by the control voltage generator, and the pass between them is:
Vc0＝Vcon；
Vc1＝Vcon+Δ；
Vc2＝Vcon+2*Δ；
The Δ representative value is 0.4V.
Vc0, Vc1 and Vc2 be connected respectively to the variable gain elementary cell control voltage input Vc0, Vc1 and Vc2 on, with reference to the accompanying drawings shown in 4.Because in same variable gain elementary cell, the source class follower of three variable gains lacks 2 resistance than top one-level, so the needed bias voltage of metal-oxide-semiconductor is respectively than the little certain voltage Δ V of upper level, design resistance and pipe sizing, make Δ V equal the DC level that this source class follower is reduced, the just directly cascade of the source class follower of such three variable gains, and do not need to use capacitance to eliminate requirement to bias voltage.
As everyone knows, the gain of the typical variable gain unit of accompanying drawing 2 the insides is not meant the number form formula to the curve of control voltage, but the Mc1 pipe just opened corresponding voltage V0 between V0+Vth in, this curved section is similar to exponential form.So will all will be similar to exponential form at the scope 0～Vdd of The whole control voltage, can only make in the accompanying drawing 4 be used for the variable resistor metal-oxide-semiconductor when Vcon when 0～Vdd progressively becomes big, pipe is progressively to open, like this in whole 0～Vdd, the gain of circuit could be similar to exponential form, could make gain be linear change with control voltage on dB.In the accompanying drawing 4, when Vcon when 0 changes to Vdd, Mc_1, Mc_2, Mc_3 pipe are progressively opened, thus on the excursion of The whole control voltage, the gain of circuit is similar to exponential form.And the excursion of control voltage is wide.
The parameter of each components and parts is as shown in table 1 in the present embodiment:
Table 1
| MOS device size (um) (W, L) | Resistance value (Ω) | |
| M1 M2 | Mc_1 Mc_2 Mc_3 | R1、R2 R3、R4 R5、R6 |
| 25 | 30 | 800 |
| 0.35 | 0.35 | |
Claims (1)
1, a kind of variable gain amplifier that is used for transmitting terminal, variable gain elementary cell and control voltage generator two parts of comprising a plurality of identical cascades, the output of said each variable gain elementary cell links to each other with the control voltage generator, it is characterized in that, said variable gain elementary cell is formed by the direct cascade of source class follower of a plurality of variable gains, wherein the source class follower of afterbody comprises: metal-oxide-semiconductor M1, M2, and as variable-resistance metal-oxide-semiconductor Mc_1, as the resistance R 1 and the R2 of biasing; Its annexation is: the output signal of previous stage is input on the grid level of M1, and another output signal of previous stage is input on the grid level of M2, and the leakage level of M1, M2 is all received on the power supply Vdd; The source class of M1 and M2 is connected the source class of Mc_1 pipe respectively and leaks level, connects respectively simultaneously on the end of R1 and R2; The other end of R1 and R2 is connected to ground; The grid level of Mc_1 is the input of control voltage input signal Vc2, and the source class end of M1 and M2 is the output of this grade signal; The formation of inferior final stage source class follower is to have increased a pair of biasing resistor R3, R4 on the basis of one-level source class follower configuration in the end and as variable-resistance metal-oxide-semiconductor Mc_2, wherein, R3 connects the end of R1, the other end ground connection of R3, R4 connects the end of R2, the other end ground connection of R4, the source of Mc_2, drain electrode connect the end of R1 and R2 respectively, also are the ends of R3 and R4 simultaneously; And the grid level of the grid level of Mc_2 and Mc_1 to link together be the input of control voltage input signal Vc1; By that analogy, the formation of previous stage source class follower all is to have increased a pair of biasing resistor and as variable-resistance metal-oxide-semiconductor on the basis of one-level source class follower configuration thereafter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021254494A CN1142634C (en) | 2002-08-09 | 2002-08-09 | Gain-variable amplifier for transmitting end |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021254494A CN1142634C (en) | 2002-08-09 | 2002-08-09 | Gain-variable amplifier for transmitting end |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1398056A CN1398056A (en) | 2003-02-19 |
| CN1142634C true CN1142634C (en) | 2004-03-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB021254494A Expired - Fee Related CN1142634C (en) | 2002-08-09 | 2002-08-09 | Gain-variable amplifier for transmitting end |
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| Country | Link |
|---|---|
| CN (1) | CN1142634C (en) |
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- 2002-08-09 CN CNB021254494A patent/CN1142634C/en not_active Expired - Fee Related
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