CN102983817B - High-gain wideband low-noise amplifier - Google Patents

Abstract

The invention relates to a high-gain wideband low-noise amplifier, which is characterized in that an active transconductance enhancing circuit is adopted, a high-frequency choke unit, a load unit, a first input amplification unit and a second input amplification unit are arranged, a radio-frequency input signal is respectively connected with the input ends of the first input amplification unit and the second input amplification unit, the output end of the first input amplification unit outputs the amplified signal to the second input amplification unit, the output end of the second input amplification unit is connected with the load unit, the load unit outputs a radio-frequency output signal, and the input end of the second input amplification unit is serially connected with the high-frequency choke unit and then is grounded.

Description

A kind of wideband low noise amplifier of high-gain

Technical field

The present invention relates to a kind of wideband low noise amplifier of high-gain, belong to radio circuit technical field, its project organization is simple, while there is larger input-output adapt ation bandwidth, improve noise and gain performance, there is good input resistant matching performance in 100M-5GHz frequency band range, have higher gain and less noise factor simultaneously.

Background technology

Low noise amplifier is the amplifier that noise factor is very low, general as the high frequency of all kinds of radio receiver or the amplifying circuit of intermediate-frequency preamplifier and high sensitivity electron detection equipment, for nearly all radio-frequency transmitter system, a requisite module is exactly low noise amplifier.The radiofrequency signal amplitude arrived due to system acceptance is usually very weak, and the noise of amplifier self may be very serious to the interference of signal, therefore wishes to reduce this noise, and provide certain voltage gain, to improve the signal to noise ratio of output.The amplifier circuit IP kernel of design high-gain, low noise has application prospect and using value comparatively widely.

Common gate structure amplifier is widely used in the design of wideband low noise amplifier, and main cause is that it has broadband Input matching characteristic, and traditional common gate structure amplifier circuit as shown in Figure 1.Signal is inputted by transistor M1 source electrode, by adjustment M1 breadth length ratio and gate bias voltage, can adjust and flow through M1 size of current, and then changes the mutual conductance gm of M1, and its input impedance is mated with 50 ohm.By adjustment load resistance R1 resistance size, different voltage gains can be obtained.This structure has wider input bandwidth sum gain bandwidth.But traditional common gate structure amplifier has following shortcoming:

First is that gain is low, and load impedance size is depended in the gain of traditional common gate structure amplifier to a great extent, but heavy load resistance can bring too much pressure drop, and limited supply voltage limits the gain of traditional common gate structure amplifier.

Second is that noise is large, and the noise factor of traditional common gate structure amplifier is comparatively large, often beyond 4dB.

3rd is that design ap-plication lacks flexibility.Traditional common grid LNA and after completing Input matching, the mutual conductance of input pipe is also determined thereupon, and the Minimum noises coefficients that circuit can realize and maximum gain also just determine, and design lacks flexibility.

In addition, have one to strengthen principle based on mutual conductance and be called as capacitive cross coupling grid LNA(CCC-CGLNA altogether) be suggested, its circuit theory diagrams are as shown in Figure 2.Realized by passive mode because its mutual conductance strengthens technology, improve less to gain and noiseproof feature.Also after having there is Input matching, the mutual conductance of input pipe has also been determined thereupon simultaneously, and design lacks flexibility.Further, it can only be used in differential signal occasion, cannot apply in single-ended signal occasion.

Summary of the invention

In order to solve the deficiency that prior art exists, the present invention proposes a kind of wideband low noise amplifier of high-gain, adopt the active broadband LNA realizing mutual conductance enhancing technology, significantly can improve gain and noiseproof feature that broadband is total to grid LNA, and input altogether bank tube mutual conductance is not subject to the restriction of Input matching, flexible design.

For achieving the above object, the present invention adopts following technical scheme:

A kind of wideband low noise amplifier of high-gain, it is characterized in that: adopt active transconductance intensifier circuit, be provided with high frequency choke unit, load unit and first, the second two input amplifying units, radio-frequency input signals connects first respectively, the input of the second two input amplifying units, amplifying signal is input to the second input amplifying unit by the output of the first input amplifying unit, the output of the second input amplifying unit connects load unit, load unit exports radio frequency output signal, the input of the second input amplifying unit is also connected ground connection after high frequency choke unit, wherein:

First input amplifying unit comprises NMOS tube M1, two resistance R1, R2, two electric capacity C1, C2, the grid of NMOS tube M1 is connected with one end of one end of resistance R1 and electric capacity C1, the other end of resistance R1 connects the first bias voltage, the other end of electric capacity C1 connects radio-frequency input signals, supply voltage is connected to after the drain series resistance R2 of NMOS tube M1, meanwhile, the drain electrode of NMOS tube M1 exports amplifying signal by electric capacity C2, the source ground of NMOS tube M1;

Second input amplifying unit comprises NMOS tube M2, resistance R3, the grid of NMOS tube M2 connects the amplifying signal output of the first input amplifying unit, and by connecting the second bias voltage after series resistance R3, the source electrode of NMOS tube M2 connects radio-frequency input signals, and the drain electrode of NMOS tube M2 is the output of the second input amplifying unit;

High frequency choke unit comprises inductance L 1, and one end of inductance L 1 is connected to the source electrode of the second input amplifying unit NMOS tube M2, and the other end of inductance L 1 receives ground;

Load unit comprises resistance R4, and one end of resistance R4 connects the output of the second input amplifying unit, and this end is also radio frequency output signal end, and the other end of resistance R4 connects supply voltage.

Advantage of the present invention and remarkable result:

(1) high-gain.Load impedance size is depended in the gain of traditional common gate structure amplifier to a great extent, but heavy load resistance can bring too much pressure drop, and limited supply voltage limits the gain of traditional common gate structure amplifier.The present invention adopts mutual conductance enhancing technology, greatly reduces the electric current of common grid LNA while completing coupling, makes under same pressure drop condition, and the value of load resistance can increase greatly, thus improves gain.And realized by active circuit because mutual conductance of the present invention strengthens technology, compare the capacitive cross coupling grid LNA altogether adopting passive mode, greatly can promote the enhancing amplitude of mutual conductance, obtain higher gain.

(2) low noise.The noise factor of traditional grid LNA altogether cannot lower than 1+ γ/α.The present invention adopts active transconductance enhancing technology, greatly reduces circuit noise coefficient.

(3) design and applying flexible.Grid LNA is after completing Input matching altogether for traditional common grid LNA and capacitive cross coupling, and the mutual conductance of input pipe is also determined thereupon, and the Minimum noises coefficients that circuit can realize and maximum gain also just determine, and design lacks flexibility.And the present invention has two parameters to supply adjustment when realizing Input matching: the gain of the first input amplifying unit and the mutual conductance of the second input amplifying unit, add the flexibility of design, can obtain optimum gain and noise factor.Capacitive cross coupling simultaneously altogether grid LNA can only be used in differential signal occasion, and the present invention both can be used in differential signal occasion, can be used in single-ended signal occasion again.

Accompanying drawing explanation

Fig. 1 is the circuit theory diagrams of traditional common gate structure low noise amplifier;

Fig. 2 is capacitive cross coupling altogether grid LNA(CCC-CGLNA) circuit theory diagrams;

Fig. 3 is circuit block diagram of the present invention;

Fig. 4 is circuit theory diagrams of the present invention;

To be the present invention compare completing the voltage gain simulation curve in Input matching situation with Fig. 1, Fig. 2 prior art Fig. 5;

To be the present invention compare completing the noise factor curve in Input matching situation with Fig. 1, Fig. 2 prior art Fig. 6;

Fig. 7,8,9 is other three kinds of implementing circuits of Fig. 4.

Embodiment

Referring to Fig. 3, the present invention is provided with high frequency choke unit, load unit and the first input amplifying unit and the second input amplifying unit, radio-frequency input signals RFin connects the input of two input amplifying units respectively, amplifying signal is input to the second input amplifying unit by the output of the first input amplifying unit, the output of the second input amplifying unit connects load unit, load unit exports radio frequency output signal RFout, and the input of the second input amplifying unit is also connected ground connection after high frequency choke unit.

Fig. 4 is the physical circuit of Fig. 3.First input amplifying unit is provided with NMOS tube M1, resistance R1, R2, electric capacity C1, C2; Second input amplifying unit comprises NMOS tube M2, resistance R3, and load unit is resistance R4, and high frequency choke unit is inductance L 1.Connect radio-frequency input signals RFin after connecting the gate series C1 of bias voltage 1, M1 after the gate series resistance R1 of M1, drain electrode contact resistance R2 is to power Vcc, and signal coupling is inputted amplifying unit to second by series capacitance C2 simultaneously.Connect bias voltage 2 after M2 gate series R3, source electrode connects radio-frequency input signals RFin and high frequency choke unit inductance L 1 of connecting arrives ground.In first input amplifying unit, the drain electrode of M1 connects the grid of M2 in the second input amplifying unit by electric capacity C2.Connect power source voltage Vcc after the drain electrode connection load resistance R4 of M2, the drain electrode of M2 exports radio frequency output signal RFout simultaneously.

In Fig. 4 circuit, the first input amplifying unit adopts common source configuration, and the second input amplifying unit adopts common gate structure, and introduces the first input amplifying unit between the source electrode and grid of the second input amplifying unit, strengthens its mutual conductance.Input signal realizes the Broadband Matching characteristic of 50 Ω input impedance by the first and second input amplifying units.Load unit is resistance.The grid of the first input amplifying unit connects input signal, source ground, and drain electrode output signal is input to the grid of the second input amplifying unit through capacitive coupling.Second input amplifying unit source electrode connect input signal and connect high frequency choke unit to, grid connects the anti-phase amplifying signal of the first input amplifying unit, play the effect that mutual conductance strengthens, integrated circuit noise can be suppressed while improving gain, reduce the noise factor of circuit, drain electrode connects load unit, and exports radiofrequency signal.

Operation principle: radio-frequency input signals is by the first and second input amplifying unit inputs, and for traditional common gate structure LNA, its input impedance is about 1/ (gm), herein, gm is the mutual conductance of common gate transistor, realize input resistant matching demand fulfillment: gm=1/Rs, Rs are source impedance.In time realizing input resistant matching, the mutual conductance of the common gate transistor of traditional common gate structure LNA is just determined thereupon.This makes when carrying out tradition and being total to grid LNA design, and gain and noiseproof feature can not get effective optimization, and design lacks flexibility.Mutual conductance enhancing technology is adopted in this patent, the first input amplifying unit is introduced between the source electrode and grid of the second input amplifying unit, mutual conductance enhancing is carried out to the M2 pipe of the second input amplifying unit, input impedance becomes: 1/ [(1+gm1R2) gm2], wherein gm1, gm2 is respectively the mutual conductance of transistor M1 and M2, and R2 is resistance value.The equivalent transconductance of circuit adds gm1R2 doubly, as long as realize input resistant matching, gm2=1/ [(1+gm1R2) Rs] just can, mutual conductance in visible second input amplifying unit altogether needed for bank tube M2 reduces (1+gm1R2) doubly, so the electric current of M2 just reduces (1+gm1R2) doubly, under same pressure drop condition, the resistance of load unit R5 just can get (1+gm1R2) of traditional common gate structure LNA doubly like this, improves the entire gain of circuit.Capacitive cross coupling altogether grid LNA can only make at most the mutual conductance inputting common bank tube narrow down to original 1/2, namely gain rises at most original 2 times, and the present invention can rise to original (1+gm1R2) doubly, gm1R2 can >>1, therefore the present invention can provide much larger than tradition grid LNA and hold the gain of cross-couplings grid LNA altogether altogether.By optimizing gm1R2, the performance of circuit can be made to be suitable for different application, to add the design flexibility of circuit simultaneously.

On the other hand, between the source electrode and grid of the second input amplifying unit, introduce the first input amplifying unit, mutual conductance enhancing is carried out to the M2 pipe of the second input amplifying unit, significantly can reduce the noise factor of circuit.

The expressions of noise that tradition is total to grid LNA is

$F=1+\frac{\mathrm{\γ}}{\mathrm{\α}}$

Wherein, α=gm/gd0, gm are device transconductance, and gd0 is the transistor channel conductance as VDS=0; γ is the coefficient relevant with bias state, and for long channel device, 2/3≤γ≤1, pipe value when saturation region is 2/3, gets 1 when linear zone zero offset, and due to hot carrier's effect, the γ value of short channel device is much larger than 1.

And its noise factor becomes after introducing active transconductance enhancing technology:

$F=1+\frac{\mathrm{\γ}}{(1+A)\mathrm{\α}}$

In above formula, A is the gain of the first input amplifying unit, is that the definition of gm1R2, α and γ is same as above in the present invention.In the calculating of this formula, have ignored the noise that the first input amplifying unit is introduced, after being taken into account by the noise of the first input amplifier, following noise factor formula can be obtained:

$F1=1+\frac{\mathrm{\γ}}{\mathrm{\α}}\frac{1}{\mathrm{gm}1R2}+\frac{\mathrm{\γ}}{\mathrm{\α}}R2\mathrm{gm}2+4\frac{\mathrm{gm}2}{\mathrm{gm}1}$

$=1+\frac{\mathrm{\γ}}{\mathrm{\α}}\frac{1}{A}+\frac{\mathrm{\γ}}{\mathrm{\α}}\frac{1}{A}\frac{R2}{\mathrm{Rs}}+4\frac{\mathrm{gm}2}{\mathrm{gm}1}$

Wherein gm1, gm2 are respectively the mutual conductance of transistor M1 and M2, and R2 is resistance value, and Rs is source impedance, and the definition of α and γ is same as above.

The noise factor of the common grid LNA of capacitive cross coupling is minimum is

$F2=1+\frac{\mathrm{\γ}}{2\mathrm{\α}}$

According to a kind of situation of our design, wherein gm1=200mS, gm2=2mS, R2=50 Ω, Rs=50 Ω, can obtain F1=1.04+0.2* γ/α, and F2=1+0.5* γ/α.In deep submicron process, γ/α is greater than 3 usually, so circuit integrity noise factor of the present invention is much smaller than traditional common grid LNA and capacitive cross coupling grid LNA altogether.

Visible referring to Fig. 5, complete the present invention in Input matching situation, traditional common grid LNA and the capacitive cross coupling comparison of grid LNA in gain altogether, it is the highest that its result shows low noise amplifier gain of the present invention.

Visible referring to Fig. 6, complete the present invention in Input matching situation, traditional common grid LNA and the capacitive cross coupling comparison of grid LNA in noise factor altogether, it is minimum that its result shows low noise amplifier of the present invention noise factor in working frequency range.

Circuit of the present invention is except can realizing by NMOS tube, also PMOS can be used to realize, its schematic diagram as shown in Figure 7, but due to larger at the area realizing PMOS in identical gain situation, small impact is had on bandwidth, but high-gain and low noise can be realized equally.Can realize with bipolar transistor equally in addition.When realizing with bipolar transistor, only need NMOS tube to replace to NPN type triode, PMOS replaces to PNP type triode.As shown in Figure 8 and Figure 9, because the Performance Ratio transistor of triode will be got well, so triode realizes obtaining circuit performance better, but its cost is also higher for specific embodiments.

Claims (1)

1. the wideband low noise amplifier of a high-gain, it is characterized in that: adopt active transconductance intensifier circuit, be provided with high frequency choke unit, load unit and first, the second two input amplifying units, radio-frequency input signals connects first respectively, the input of the second two input amplifying units, amplifying signal is input to the second input amplifying unit by the output of the first input amplifying unit, the output of the second input amplifying unit connects load unit, load unit exports radio frequency output signal, ground connection after the input series connection high frequency choke unit of the second input amplifying unit, wherein:

First input amplifying unit comprises NMOS tube M1, two resistance R1, R2, two electric capacity C1, C2, the grid of NMOS tube M1 is connected with one end of one end of resistance R1 and electric capacity C1, the other end of resistance R1 connects the first bias voltage, the other end of electric capacity C1 connects radio-frequency input signals as the input that first inputs amplifying unit, supply voltage is connected to after the drain series resistance R2 of NMOS tube M1, simultaneously, the drain electrode of NMOS tube M1 exports amplifying signal by electric capacity C2, namely the output of electric capacity C2 is the output of the first input amplifying unit, the source ground of NMOS tube M1,

Second input amplifying unit comprises NMOS tube M2, resistance R3, the grid of NMOS tube M2 connects the first input amplifying signal output of amplifying unit and output of electric capacity C2, and by connecting the second bias voltage after series resistance R3, the source electrode of NMOS tube M2 connects radio-frequency input signals as the input that second inputs amplifying unit, and the drain electrode of NMOS tube M2 is the output of the second input amplifying unit;

High frequency choke unit comprises inductance L 1, and one end of inductance L 1 is connected to the source electrode of the second input amplifying unit NMOS tube M2, and the other end of inductance L 1 receives ground;

Load unit comprises resistance R4, and one end of resistance R4 connects the output of the second input amplifying unit, and this end is also radio frequency output signal end, and the other end of resistance R4 connects supply voltage.