CN105305979A

CN105305979A - Distributed amplifier circuit for perfecting linearity

Info

Publication number: CN105305979A
Application number: CN201510737532.8A
Authority: CN
Inventors: 张瑛
Original assignee: Nanjing Post and Telecommunication University
Current assignee: Nanjing Post and Telecommunication University; Nanjing University of Posts and Telecommunications
Priority date: 2015-11-03
Filing date: 2015-11-03
Publication date: 2016-02-03
Anticipated expiration: 2035-11-03
Also published as: CN105305979B

Abstract

The invention discloses a distributed amplifier circuit for perfecting linearity. The distributed amplifier circuit comprises a plurality of gain units, an input on-chip inductor connected to an input end of each gain unit, and an output on-chip inductor connected to an output end of each gain unit, wherein an interstage matching capacitor is arranged in front of or behind at least one input on-chip inductor, the input end of each gain unit is connected with a biasing resistor, and a bias voltage is applied from the other end of the biasing resistor. According to the distributed amplifier circuit for perfecting linearity disclosed by the invention, the gain units of different circuit structures are adopted, different bias voltages are applied to change the static working points of the gain units so as to change the linearity thereof, the interstage matching capacitor is introduced to offset and isolate direct current at the input ends of the gain units, so that different bias voltages can be applied to the input ends of the gain units, and then the degree of freedom of design and debugging is increased.

Description

A kind of distributed amplifier circuit improving the linearity

Technical field

The invention belongs to technical field of integrated circuits, particularly a kind of distributed amplifier circuit improving the linearity.

Background technology

The develop rapidly of wireless communication technology proposes requirements at the higher level to the data transmission rate of communication system and bandwidth.The wide-band amplifier designing technique of usual employing comprises negative feedback, balance amplifier, resistors match and active matching etc., but these technology all cannot the gain bandwidth product of effective boost amplifier.Distributed amplifier is due to its structural characteristic, the restriction that amplifier gain bandwidth is long-pending can be broken through, realize more wide band signal to amplify, be widely used in ultra broadband MMIC (MonolithicMicrowaveIntegratedCircuit, the monolithic integrated microwave circuit) field comprising microwave power amplifier.There is various types of structure in current distributed amplifier, comprise heterogeneous texture, distribution-cascade structure etc., but they are all the artificial transmission line's forms adopting lowpass structures, under now all gain units all must operate at same bias state, therefore design freedom is lower, cannot improve the performances such as the linearity of distributed amplifier by arranging different working points.

The general principle of distributed amplifier is that the parasitic capacitance of transistor and inductance element are formed artificial transmission line, thus overcomes the roll off of gain that parasitic capacitance causes, and as shown in Figure 1, wherein VDD is supply voltage to its circuit theory diagrams, V _gfor DC offset voltage, on-chip inductor L _giinput artificial transmission line is constituted, on-chip inductor L with the input impedance of gain unit _diconstitute with the output impedance of gain unit and export artificial transmission line, obvious I/O artificial transmission line is low-pass filter structure.Traditional distributed amplifier due to gain per stage unit adopt direct coupling system, under therefore each gain unit must operate at same direct current biasing condition.

Summary of the invention

In view of above-mentioned deficiency of the prior art, the present invention proposes a kind of distributed amplifier circuit improving the linearity, and its technical scheme is:

A kind of distributed amplifier circuit improving the linearity, comprise several gain units and be connected to the input on-chip inductor of each described gain unit input, be connected to the output on-chip inductor of each described gain unit output, interstage matched electric capacity was provided with input on-chip inductor described at least one before or after, the input of each described gain unit is connected with biasing resistor, applies bias voltage from the other end of described biasing resistor.

Preferably, before each described input on-chip inductor, interstage matched electric capacity is provided with.

Before first described output on-chip inductor, export on-chip inductor with last be in series with a coupling capacitance respectively.

Described gain unit is a NMOS tube, and its grid is input, drains as output.

Described gain unit is made up of the NMOS tube that two connect, and the source electrode of the first NMOS tube is connected with the drain electrode of the second NMOS tube, and the grid of the second NMOS tube is input, and the drain electrode of the first NMOS tube is output.

Described gain unit is made up of two NMOS tube and an inductance, the source electrode of the first NMOS tube is connected with described inductance one end, the other end of described inductance connects the drain electrode of the second NMOS tube, and the grid of the second NMOS tube is input, and the drain electrode of the first NMOS tube is output.

The present invention is by adopting the gain unit of different circuit structure, and apply the quiescent point that different bias voltages can change each gain unit, thus their linearity can be improved, the direct current biasing of each gain unit input is kept apart by the introducing of interstage matched electric capacity, thus different bias voltages can be applied to the input of each gain unit, thus add the degree of freedom of design and layout.

Accompanying drawing explanation

Fig. 1 is traditional distributed amplifier circuit structure diagram;

Fig. 2 is embodiment of the present invention distributed amplifier circuit structure diagram;

Fig. 3 is an example structure figure of gain unit in Fig. 2;

Fig. 4 is another example structure figure of gain unit in Fig. 2;

Fig. 5 is another example structure figure of gain unit in Fig. 2;

Fig. 6 is the relation of the output current of Fig. 3 embodiment, transadmittance gain and all-order derivative and input voltage;

Fig. 7 is the relation of the output current of Fig. 4 and Fig. 5 embodiment, transadmittance gain and all-order derivative and input voltage.

Embodiment

In order to make object of the present invention, technical scheme and advantage clearly understand, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.

As shown in Figure 2, compared with the traditional distributed amplifier shown in Fig. 1, there are following three places and improve in distributed amplifier circuit structure of the present invention:

(1) before or after at least one input on-chip inductor, interstage matched electric capacity is provided with, with L _gicommon formation band leads to matching network, at each input on-chip inductor L in Fig. 2 _gibefore be connected with electric capacity C _gi, in fact C _gialso L can be placed on _giafterwards; C _giquantity be [1, N];

(2) have employed independently bias structure R at the input of the gain unit being provided with interstage matched electric capacity _gi, different bias voltage V can be applied to the input of gain unit with this _gi;

(3) gain unit can adopt any one circuit structure as shown in Fig. 3 to Fig. 5, but generally all adopts identical circuit structure in same circuit.

The principle of distributed amplifier circuit of the present invention is as follows:

The output current i of gain unit _owith input offset voltage v _inbetween always there is following relational expression

i_{o} = g_{m} v_{i n} + g_{m}^{'} v_{i n}^{2} + g_{m}^{''} v_{i n}^{3}

Wherein g _mrepresent the transadmittance gain of gain unit, g ' _mfor i _oabout v _insecond dervative, g " _mfor i _oabout v _inthree order derivatives.

Theoretical according to radio circuit, g " _mmaximum to the linearity performance impact of amplifier, g _mwhen certain, g " _mthe linearity of less then amplifier is better.Relation between the transconductance characteristic of the gain unit of different structure and input offset voltage as shown in Figure 6 and Figure 7.

As shown in Figure 3, a kind of structure of gain unit is a NMOS tube, and its grid is input, drains as output, adopt the distributed amplifier circuit output current of this structure, transadmittance gain and all-order derivative and input voltage relation as shown in Figure 6.Can find out that gain unit presents by Fig. 6 (b) serious non-linear, i.e. transadmittance gain g _mnot constant value, but along with input offset voltage v _inchange and change, therefore when amplifier input signal amplitude increase time, output signal will there is nonlinear distortion.

As shown in Figure 4, the another kind of structure of gain unit is: gain unit is made up of the NMOS tube that two connect, and the source electrode of the first NMOS tube is connected with the drain electrode of the second NMOS tube, and the grid of the second NMOS tube is input, and the drain electrode of the first NMOS tube is output.

As shown in Figure 5, another structure of gain unit is: gain unit is made up of two NMOS tube and an inductance, the source electrode of the first NMOS tube is connected with inductance one end, the other end of inductance connects the drain electrode of the second NMOS tube, the grid of the second NMOS tube is input, the drain electrode of the first NMOS tube is output, and this inductance is peak value inductance.Adopt the distributed amplifier circuit output current of Fig. 4 and Fig. 5 two kinds of structures, transadmittance gain and all-order derivative and input voltage relation as shown in Figure 7.Can find out that gain unit presents equally by Fig. 7 (a) (b) serious non-linear, i.e. transadmittance gain g _mnot constant value, but along with input offset voltage v _inchange and change, therefore when amplifier input signal amplitude increase time, output signal will there is nonlinear distortion.

According to the operation principle of distributed amplifier, its forward direction transadmittance gain is the superposition of each gain unit transadmittance gain, therefore as can be seen from Fig. 6 (d) and Fig. 7 (d), when each gain unit adopt identical (or different) circuit structure and when being in different input offset voltages, g " _mcan get on the occasion of also can negative value be got, therefore only need by regulating the bias voltage of each gain unit that the second order local derviation of total transadmittance gain of distributed amplifier just can be made to level off to zero, thus obtain the good linearity.

Technological means disclosed in the present invention program is not limited only to the technological means disclosed in above-mentioned execution mode, also comprises the technical scheme be made up of above technical characteristic combination in any.

Claims

1. one kind is improved the distributed amplifier circuit of the linearity, comprise several gain units and be connected to the input on-chip inductor of each described gain unit input, be connected to the output on-chip inductor of each described gain unit output, it is characterized in that: input on-chip inductor described at least one before or after, be provided with interstage matched electric capacity, the input of each described gain unit is connected with biasing resistor, applies bias voltage from the other end of described biasing resistor.

2. distributed amplifier circuit according to claim 1, is characterized in that: before each described input on-chip inductor, be provided with interstage matched electric capacity.

3. distributed amplifier circuit according to claim 1, is characterized in that: before first described output on-chip inductor, export on-chip inductor with last be in series with a coupling capacitance respectively.

4. distributed amplifier circuit according to claim 1, is characterized in that: described gain unit is a NMOS tube, and its grid is input, drains as output.

5. distributed amplifier circuit according to claim 1, it is characterized in that: described gain unit is made up of the NMOS tube that two connect, the source electrode of the first NMOS tube is connected with the drain electrode of the second NMOS tube, and the grid of the second NMOS tube is input, and the drain electrode of the first NMOS tube is output.

6. distributed amplifier circuit according to claim 1, it is characterized in that: described gain unit is made up of two NMOS tube and an inductance, the source electrode of the first NMOS tube is connected with described inductance one end, the other end of described inductance connects the drain electrode of the second NMOS tube, the grid of the second NMOS tube is input, and the drain electrode of the first NMOS tube is output.