CN103580614A

CN103580614A - Low-noise amplifier

Info

Publication number: CN103580614A
Application number: CN201210253229.7A
Authority: CN
Inventors: 陈宪谷; 张家润; 陈家源; 林盈熙
Original assignee: Realtek Semiconductor Corp
Current assignee: Realtek Semiconductor Corp
Priority date: 2012-07-20
Filing date: 2012-07-20
Publication date: 2014-02-12
Anticipated expiration: 2032-07-20
Also published as: CN103580614B

Abstract

The invention discloses a low-noise amplifier which comprises a transformer and a first-stage gain circuit, wherein the transformer is provided with a primary coil and a secondary coil, and the primary coil is used for receiving an input signal. The first-stage gain circuit is provided with a first input port which is coupled to the primary coil, and the first-stage gain circuit is used for proving grain to the input signal to generate first output.

Description

Low noise amplifier

Technical field

The present invention, about wireless communication field, refers in particular to a kind of low noise amplifier for receiver.

Background technology

In wireless communication system, receiver need to pass through low noise amplifier (low noise amplifier, LNA), and the wireless signal receiving from antenna is amplified, and for follow-up demodulator, carries out demodulation process.Low noise amplifier must be considered a lot of aspects in design, and what be even more important is exactly the noise self causing.If in the process of amplifying radio signals, too much noise is brought into wireless signal, can cause demodulator to produce wrong demodulation result.That is to say, low noise amplifier must possess enough low noise figure (noise figure) in design, just can guarantee the correctness of transfer of data.On the other hand, under the trend of integrated circuit micro, the design of low noise amplifier also must be considered how in limited circuit area, by low noise amplifier optimizing effect.Therefore, how to design and have small electric road surface low noise amplifier long-pending and better noise resisting ability concurrently and just become the important ring in wireless communication system.

Summary of the invention

In view of this, an object of the present invention is to provide a kind of long-pending noiselike signal amplifier in small electric road surface that has, and it is mainly by integrating the subelement in amplifier to reach.In addition, the noise that another object of the present invention is to utilize the transformer of input to come step-down amplifier itself to bring, reaches good noise suppression effect.

Embodiments of the invention provide a kind of amplifier, and this amplifier comprises: a transformer and a first order gain circuitry.This transformer has main coil and a less important coil, and this main coil is in order to receive an input signal.This first order gain circuitry has a first input end mouth, and this first input end mouth is coupled to this main coil.And this first order gain circuitry is in order to provide a gain to produce one first output to this input signal.

Accompanying drawing explanation

Fig. 1 is the circuit framework figure of an embodiment of amplifier of the present invention;

Fig. 2 illustrates the end points polarity of the transformer in amplifier of the present invention;

Fig. 3 illustrates an enforcement winding mode of the transformer in amplifier of the present invention.

Wherein, description of reference numerals is as follows:

100 amplifiers;

120 transformers;

140,160 gain circuitries;

122,124,180 coils;

M1 ~ M4 transistor.

Embodiment

At specification and in the middle of applying for a patent claim scope, used some vocabulary to censure specific element.In affiliated field, technical staff should understand, and hardware manufacturer may be called same element with different nouns.This specification and the follow-up claim scope of applying for a patent are not used as distinguishing the mode of element with the difference of title, but the difference in function is used as the criterion of distinguishing with element.Mentioned in the middle of specification and claim in the whole text " comprise " be an open term, therefore should be construed to " comprise but be not limited to ".In addition; " coupling " word comprises directly any and is indirectly electrically connected means at this; therefore; if describe a first device in literary composition, be coupled to one second device; represent that this first device can directly be electrically connected in this second device, or be indirectly electrically connected to this second device by other devices or connection means.

Please refer to Fig. 1, the circuit framework figure of its embodiment who is amplifier of the present invention.As shown in the figure, amplifier 100 can provide a gain to an input signal Si n, to produce an output signal Sout.Amplifier 100 comprises a transformer 120 and a first order gain circuitry 140.Transformer 120 includes a main coil 122 and a less important coil 124.The second end of the first end of main coil 122 and main coil 122 is respectively coupled to first input end N1 and the second input N2 of a first input end mouth of first order gain circuitry 140.Moreover the second end of the first end of less important coil 124 and less important coil 124 is respectively coupled to the 3rd input N3 and four-input terminal N4 of one second input port of first order gain circuitry 140.When the input signal Si n of the single-ended format first end (or saying input N1) by main coil 122 inputs to transformer 120, based on Lenz's law, second end (or saying input N2) of main coil 122 will produce the signal anti-phase with input signal Si n, thus, just can on the first input end mouth of first order gain circuitry 140, form one group of differential wave.Moreover, the signal coupling effect providing by transformer 120, the main coil 122 formed differential input signals in two ends can be coupled to the 3rd input N3 and four-input terminal N4 of the second input port of first order gain circuitry 140, thus, transistor M1 in first order gain circuitry 140 and the equivalence of M2 transduction will be enhanced, and then the channel noise that brings when 140 pairs of these group differential waves of first order gain circuitry are amplified of inhibition.

In one embodiment of the invention, main coil 122 has again a tap terminals (tap) X5, is coupled to one first reference voltage (as: earthed voltage GND), and wherein tap terminals X5 may be a center tap end (center tap).In addition, less important coil 124 also has a tap terminals X6, is coupled between one second reference voltage (as: bias voltage Vbias1), and wherein tap terminals X6 may be a center tap end.Yet the connected mode shown in above-described specific annexation and Fig. 1 is not restriction of the present invention.

In addition, first order gain circuitry 140 includes the first field-effect transistor M1 and the second field-effect transistor M2, and wherein the annexation of each electrode of transistor and transformer 120 is as follows.The control electrode of the control electrode of the first field-effect transistor M1 (as: grid) and the second field-effect transistor M2 is used as respectively the 3rd input N3 and four-input terminal N4 of the second input port of first order gain circuitry 140, and is coupled to less important coil 124.In addition, the first electrode (as: source electrode) of the first field-effect transistor M1 and the first electrode of the second field-effect transistor M2 are used as respectively first input end N1 and the second input N2 of the first input end mouth of first order gain circuitry 140, and are coupled to main coil 122.Connected mode by above, has suppressed channel noise, so first order gain circuitry 140 can produce an output signal S_out_ini who has less noise or do not have noise.

In one embodiment of the invention, amplifier 100 includes again a second level gain circuitry 160, in order to provide a gain to the output signal S_out_ini exporting from first order gain circuitry 140, produce output signal S_out, and output signal S_out is offered to follow-up signal processing circuit.Yet, this non-restriction of the present invention, in other embodiments of the invention, amplifier 100 may only include first order gain circuitry 140, and therefore amplifier 100 directly provides output signal S_out_ini to follow-up signal processing circuit.Wherein, second level gain circuitry 160 includes one the 3rd field-effect transistor M3 and one the 4th field-effect transistor M4, detailed annexation as shown in Figure 1, the control electrode of the 3rd field-effect transistor M3 and the 4th field-effect transistor M4 is connected to a bias voltage Vbias2, wherein, bias voltage Vbias2 may be same or different from bias voltage Vbias1.On the second electrode (as: drain) of the 3rd field-effect transistor M3 and the second electrode of the 4th field-effect transistor M4, the output signal S_out of differential pattern will be produced.In addition, in one embodiment of the invention, the second electrode of the second electrode of the 3rd field-effect transistor M3 and the 4th field-effect transistor M4 may be as shown in Figure 1 as, be connected to the two ends of a tertiary coil 180, wherein, tertiary coil 180 is used as an inductive load of amplifier 100.

Please note, although field-effect transistor M1, M2 in embodiment mentioned above, M3, M4 are N-type field-effect transistor, yet, this non-restriction of the present invention, in other embodiments of the invention, also can adopt the combination of P type field-effect transistor or N-type field-effect transistor and P type field-effect transistor to realize first order gain circuitry 140 and second level gain circuitry 160.

In order to reach antimierophonic good result, in one embodiment of the invention, the polarity of main coil 122 as having as shown in Figure 2 with less important coil 124.Fig. 2 indicates the signal polarity of coil end points based on a rule (dot convention).As shown in the figure, the first end (or perhaps end points N1) of main coil 122 is the approach axis of voltage/current, the second end of less important coil 124 (or perhaps end points N4) is the outbound course of voltage/current, that is to say, the main first end (or perhaps end points N1) of coil 122 and the first end (or perhaps end points N3) of less important coil 124 have different signal polarities.Thus, main coil 122 just can reduce channel noise or other the possible noises that field-effect transistor (M1, M2, M3, M4) causes by coupling effect with less important coil 124, reaches the effect of noise suppressed.Yet the polar configurations mode shown in Fig. 2 that it should be noted in the discussion above that not is the unique possible execution mode of the present invention, in other embodiments of the invention, still may there is other polar configurations mode, reach the effect of noise reducing.

A possibility winding mode about transformer 120 on circuit layout please refer to Fig. 3.As shown in the figure, the two ends of main coil 122 are respectively coupled to first input end N1 and the second input N2 of first order gain circuitry 140, and the two ends of less important coil 124 are respectively coupled to the 3rd input N3 and four-input terminal N4 of first order gain circuitry 140.Moreover the tap terminals X5 of main coil 122 is coupled to earthed voltage GND, and the tap terminals X6 of less important coil 124 is coupled to bias voltage Vbias1.In addition, the conducting path of the coiling of main coil 122 and less important coil 124 in illustrating forms.Note that the winding mode shown in Fig. 3 is not the unique possible winding mode of transformer 120 of the present invention, any other can be reached with the winding mode of transformer 120 same effect and all belong to category of the present invention.

With above mentioned " embodiment " representative for the described special characteristic of this embodiment, structure or characteristic, be contained at least one execution mode of the present invention.In other words, in literary composition, in different paragraphs, occur " embodiment " not represent identical embodiment.Therefore,, although while describing for different embodiment above, mentioned respectively the action of different architectural feature or method, it should be noted in the discussion above that these different characteristics can be implemented in same specific embodiment by suitable modification simultaneously.

In practical application, signal gain circuit 100 can be usingd as the low noise amplifier circuit in this receiver in a wireless receiver, and transformer 120 can be realized it by a balanced-unbalanced transformer (balun).In general, low noise amplifier need carry out by balanced-unbalanced transformer (balun) conversion (wireless signal receiving due to antenna is generally single-ended pattern) of single-ended/differential input signal, and also may need to provide a high input impedance (being conventionally arranged between transistorized source electrode and earth terminal) by inductive element simultaneously.Because inductive element has conventionally accounted for appreciable space on circuit layout, therefore such framework often has sizable circuit area.The present invention carries out the conversion of single-ended/differential input signal by the main coil 122 of balanced-unbalanced transformer, and also by main coil 122, provide high input impedance to amplifier 100, therefore, the circuit area of amplifier 100 can be maintained to a desirable amount.In addition, the present invention is connected to the less important coil 124 of transformer 120 transistor (the M1 in the first order gain circuitry 140 of amplifier, M2) grid, thus, just by the signal coupling effect between coil and coil, eliminate noise, finally can, in effective circuit area, realize the low noise amplifier with superperformance.

The foregoing is only preferred embodiment of the present invention, all equalizations of doing according to the present patent application Patent right requirement scope change and modify, and all should belong to covering scope of the present invention.

Claims

1. an amplifier, is characterized in that, comprises:

One transformer, has main coil and a less important coil, and this main coil is in order to receive an input signal; And

One first order gain circuitry, has a first input end mouth, and this first input end mouth is coupled to this main coil, and this first order gain circuitry is in order to provide a gain to produce one first output to this input signal.

2. amplifier as claimed in claim 1, is characterized in that, this first order gain circuitry includes a first transistor and a transistor seconds, and each transistor includes a control electrode, one first electrode and one second electrode.

3. amplifier as claimed in claim 2, is characterized in that, this first input end mouth includes:

One first input end, is coupled to a first end of this main coil; And

One second input, is coupled to one second end of this main coil;

Wherein the first electrode of this first transistor and the first electrode of this transistor seconds are respectively as this first input end and this second input.

4. amplifier as claimed in claim 3, is characterized in that, this first order gain circuitry separately has one second input port, and this second input port includes:

One the 3rd input, is coupled to a first end of this less important coil; And

One four-input terminal, is coupled to one second end of this less important coil;

Wherein the control electrode of this first transistor and the control electrode of this transistor seconds are respectively as the 3rd input and this four-input terminal.

5. amplifier as claimed in claim 4, is characterized in that, the polarity of this first end of this main coil is different from the polarity of this first end of this less important coil.

6. amplifier as claimed in claim 1, is characterized in that, this transformer is a balanced-to-unblanced transformer.

7. amplifier as claimed in claim 1, is characterized in that, this main coil includes a tap terminals and is coupled to one first reference voltage level, and this less important coil includes a tap terminals and is coupled to one second reference voltage level.

8. amplifier as claimed in claim 1, is characterized in that, separately includes:

One second level gain circuitry, is coupled to this first order gain circuitry, in order to receive this first output, and produces one second output.

9. amplifier as claimed in claim 8, is characterized in that, separately includes:

One tertiary coil, is coupled to this second level gain circuitry, in order to as an inductive load.

10. amplifier as claimed in claim 1, is characterized in that, it is arranged in a receiver.