CN103414439B - A Fully Differential Power Current Amplifier with Noise Cancellation Circuit - Google Patents

Abstract

The invention discloses a fully differential power current amplifier with a noise cancellation circuit, which is composed of a full differential power current amplifier body and a noise cancellation circuit. Wherein, the fully differential power current amplifier is composed of two sets of identical Nullors, current parallel negative feedback networks, and current series negative feedback networks to form a symmetrical differential structure, and wherein the current series negative feedback network is realized by a transformer, and the current The parallel negative feedback network is realized by a single resistor; the noise cancellation circuit is composed of two groups of identical noise current detection stages, current-voltage conversion stages, voltage-current conversion stages and mixed current synthesis stages that are cascaded in sequence, and each The group noise canceling circuit corresponds to the half-side circuit of the above-mentioned fully differential power current amplifier. The invention can reduce the noise of the transformer feedback network in the full differential power amplifier.

Description

A Fully Differential Power Current Amplifier with Noise Cancellation Circuit

technical field

The invention belongs to the technical field of analog integrated circuits, and in particular relates to a fully differential power current amplifier with a noise cancellation circuit.

Background technique

The output signal of the fully differential power current amplifier is a differential current. When it has a large enough gain, it can directly drive the switch stage of the mixer, eliminating the transconductance stage of the mixer, thus forming a new type of RF front-end circuit, compared with the traditional RF front-end current, the circuit has higher linearity, process consistency and robustness.

However, since the noise contribution of the feedback network in the power current amplifier is relatively large (accounting for about 20%, see reference [1]), when a symmetrical differential structure is formed, the noise of the feedback network is also doubled correspondingly, resulting in the noise of the entire amplifier Noise performance is severely constrained by the feedback network. In order to reduce the noise contribution of the feedback network (especially the current parallel negative feedback network, such as realized with a transformer) in the fully differential power current low noise amplifier, the present invention proposes a method for offsetting the noise generated by the passive differential current parallel negative feedback network .

At present, there is no relevant literature introduction, and no relevant patent documents have been found.

references

[1] Xiaolong Li and Wouter A.Serdijn, "On the Design of BroadbandPower-to-Current Low Noise Amplifiers," IEEE Transactions on Circuits and Systems-I: Regular Papers, vol.59, no.3, pp.493-504 , March 2012.

Contents of the invention

The technical problem to be solved by the object of the present invention is to provide a fully differential power current amplifier with a noise canceling circuit for the defects of the prior art.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A fully differential power current amplifier with a noise canceling circuit, comprising a fully differential power current amplifier body and a noise canceling circuit, the noise canceling circuit is composed of two canceling branches with the same structure, and each canceling branch has It consists of cascaded current detection stage, current-voltage conversion stage, voltage-current conversion stage and mixed current synthesis stage; the signal source is connected to the input end of the current detection stage of the fully differential power current amplifier body and each offset branch respectively connection, the output end of the fully differential power current amplifier body is respectively connected to the input end of the mixed current synthesis stage of each cancellation branch, and the output terminal of the mixed current synthesis stage of each cancellation branch is respectively connected to the load.

The fully differential power current amplifier body is composed of two amplification branches with the same structure, each amplification branch is set corresponding to the offset branch, and each amplification branch is composed of Nullor, current parallel negative feedback network, and current series negative feedback network. The feedback network is formed; the current parallel negative feedback network is respectively the first and second transformers, and the current series negative feedback network is the first and second resistors; the terminal with the same name of the primary coil of the above-mentioned first transformer and the The inverting output terminal is connected, the same-named terminal of the secondary coil of the first transformer is respectively connected with the in-phase input terminal of the first Nullor and the signal source; the different-named terminal of the primary coil of the first transformer is connected with the input terminal of the corresponding mixed current synthesis stage , the opposite end of the secondary coil of the first transformer is grounded; one end of the first resistor is connected to the inverting input end and the non-inverting output end of the first Nullor.

The same-named end of the primary coil of the second transformer is connected to the inverting output end of the second Nullor, and the same-named end of the secondary coil of the second transformer is respectively connected to the non-inverting input end and the signal source of the second Nullor; the second transformer primary coil The opposite end of the second resistor is connected to the input end of the corresponding mixed current synthesis stage, and the opposite end of the second transformer secondary coil is grounded; one end of the second resistor is connected to the inverting input end and the non-inverting output end of the second Nullor; the first, The other ends of the second resistors are connected to each other.

The current detection stage uses a current sensor or an integrated transformer.

The hybrid current synthesis stage uses a current adder or subtractor.

The current-voltage conversion stage adopts a passive or active current-voltage conversion circuit.

A kind of fully differential power current amplifier with noise cancellation circuit of the present invention has following advantage and beneficial effect:

1. Since a kind of fully differential power current amplifier of the present invention can offset the noise of the current parallel negative feedback network, it can reduce the noise contribution of the current parallel negative feedback network to the amplifier, thereby improving the noise performance of the entire amplifier.

2. Since the noise cancellation circuit of the present invention has a fully differential power current amplifier detects and processes differential current signals, the introduction of the noise cancellation circuit will not affect the topology of the original differential power current amplifier.

3. Since a kind of noise canceling circuit with full differential power current amplifier of the present invention constitutes a symmetrical differential structure, after the information signals output by its two symmetrical mixed current synthesis stages are superimposed, it maintains a higher gain while increasing the gain. common-mode rejection ratio, process consistency and robustness.

Description of drawings

Fig. 1 is a schematic diagram of the principle of the present invention.

FIG. 2 is a schematic diagram of a specific implementation of FIG. 1 .

In Figure 1 and Figure 2: 10, 20. Current detection stage, 11, 21. Current-voltage conversion stage 12, 22. Voltage-current conversion stage, 13, 23. Mixed current synthesis stage, 30, 40. Nullor, 31 , 41. Transformer.

detailed description

In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with the embodiments and accompanying drawings.

As shown in Figure 1, a fully differential power current amplifier with a noise canceling circuit is composed of a fully differential power current amplifier body and a noise canceling circuit. Wherein, the fully differential power current amplifier body is composed of two identical groups of Nullors, current parallel negative feedback networks, and current series negative feedback networks to form a symmetrical differential structure, and wherein the current series negative feedback network is realized by a transformer, The current parallel negative feedback network is realized by a single resistor; the noise cancellation circuit is composed of two groups of identical noise current detection stages, a current-voltage conversion stage, a voltage-current conversion stage and a mixed current synthesis stage which are cascaded in sequence, And each group of noise canceling circuits corresponds to the half-side circuit of the above-mentioned fully differential power current amplifier.

The above-mentioned current detection stages 10, 20, current-voltage conversion stages 11, 21, voltage-current conversion stages 12, 22 and Nullor 30, 40 are all four-port networks, that is, they each have two input ports and two output ports The above-mentioned current parallel negative feedback network is realized by the first and second transformers 31, 41, the above-mentioned current series negative feedback network is composed of the first and second resistors 32, 42, and the above-mentioned mixed current synthesis stage 13, 23 is A five-port network in which two are output ports and three are input ports, and one of the input ports is a common to the other two input ports.

The current parallel negative feedback network is the first and second transformers 31 and 41 respectively, the current series negative feedback network is the first and second resistors 32 and 42, and the terminal with the same name of the primary coil of the first transformer 31 is connected to the first The inverting output end of a Nullor30 is connected, and the same-named end of the primary coil of the first transformer 31 is respectively connected with the non-inverting input end and the signal source of the first Nullor30; the same-named end of the first transformer 31 secondary coil is connected with the corresponding mixed current synthesis The input terminals of the first transformer 31 are connected to each other, and the opposite end of the secondary coil of the first transformer 31 is grounded; one end of the first resistor 32 is connected to the inverting input terminal and the non-inverting output terminal of the first Nullor 30;

The above-mentioned second Nullor 40 and the second transformer 41 are in one-to-one correspondence with the above-mentioned first Nullor 30 and the first transformer 31 and are connected in the same way.

The specific connection mode of the noise cancellation circuit is: the above-mentioned current detection stage 10, current-voltage conversion stage 11, voltage-current conversion stage 12, and mixed current synthesis stage 13 are cascaded in sequence, that is, the current detection stage 10 The two output terminals are connected to the two input terminals of the current-voltage conversion stage 11, the output terminals of the current-voltage conversion stage 11 are connected to the input terminals of the voltage-current conversion stage 12, and the voltage-current conversion stage The output end of 12 is connected with the input terminal of described mixed current synthesis stage 13, and one of the input ports of described mixed current synthesis stage 13 is a common end, grounding; One of the output ports of above-mentioned mixed current synthesis stage 13 and load One end is connected, and the other output port is grounded.

The above-mentioned current detection stage 20, current-voltage conversion stage 21, voltage-current conversion stage 22, and mixed current synthesis stage 23 are connected in the same manner as the above-mentioned current detection stage 10, current-voltage conversion stage 11, voltage-current conversion stage 12, The mixed current synthesis stages 13 correspond to each other and are connected in the same way.

The specific connection mode between the above-mentioned fully differential power current amplifier and the noise cancellation circuit is: the input terminal of the current detection stage 10/20 in the noise cancellation circuit is respectively connected to a differential input terminal of the signal source and the differential power current amplifier. The non-inverting input terminal of the Nullor 30/40 is connected; the non-inverting terminal of the transformer 31/41 in the fully differential power current amplifier is connected with the remaining input port of the hybrid current synthesis stage 13/23 of the noise canceling circuit.

The above-mentioned voltage-current conversion stage can be realized by using a passive or active voltage-current conversion circuit.

The above mixed current synthesis stage can be realized by a current adder or a current subtractor with differential output.

FIG. 2 is a specific implementation circuit diagram of a fully differential power current amplifier with a noise canceling circuit shown in FIG. 1 . Nullor 30 in Figure 1 is realized in Figure 2 by a two-stage amplifier composed of transistors VF301, VF302, and VF303, where its input stage is composed of a common-source amplifier VF301, and its output stage is composed of a fully differential amplifier VF302 and VF303; Fig. 1 Nullor40 in Figure 2 is realized by a two-stage amplifier composed of transistors VF401, VF402 and VF403, in which its input stage is composed of common source amplifier VF401, and its output stage is composed of fully differential amplifiers VF402 and VF403. The two transformers 31 and 41 in FIG. 1 are both realized by integrated transformers with a turn ratio of 1:N, and are respectively marked as TF311 and TF411 in FIG. 2 . The single resistor in FIG. 1 is composed of two resistors R ₂₂₁ and R ₂₁₁ with a resistance value of R/2 connected in series in FIG. 2 . The current detection stages 10 and 20 in FIG. 1 are both implemented by integrated transformers with a turn ratio of 1:1, which are respectively marked as TF101 and TF201 in FIG. 2 . The current-voltage conversion stage 11 in Fig. 1 is realized by R ₁₁₁ in Fig. 2; the current-voltage conversion stage 21 in Fig. 1 is realized by R ₂₁₁ in Fig. 2, and the voltage-current conversion stage 12 and hybrid The current synthesis stage 13 is composed of VF121 in Fig. 2 (indicated by VF121/VF131 in the figure), and the voltage-current conversion stage 22 and mixed current synthesis stage 23 in Fig. 1 are all composed of VF221 in Fig. 2 (indicated by VF121 in the figure). VF221/VF231 marked), wherein resistors R ₁₂₁ , R ₁₂₂ and R ₂₂₁ , R ₂₂₂ provide bias voltages for VF121/VF131 and VF221/VF231 respectively.

Approximate workflow of a fully differential power current amplifier with noise cancellation circuit:

Differential power signals (u _in+ , u _in - and i _in+ , i _in- ) are input to the primary coils of TF101 and TF201, and the current signals detected at the opposite ends of the secondary coils are converted into voltages by resistors R ₁₁₁ and R ₂₁₁ respectively. The voltage signal is amplified by transconductance amplifier stages VF121/VF131 and VF221/VF231 and then converted into output current; at the same time, the current signal output by the primary coil of TF101/TF201 is converted into output current by transconductance amplifier stage VF301/VF401. The polarity of the information voltage signal at nodes X and Z is the same, but opposite to that of the information voltage signal at node Y; the polarity of the noise voltage signal at nodes Z and Y is the same, but the polarity of the noise voltage signal at node X is the same Sex is the opposite. Therefore, the information signals at the input terminals of VF121/VF131 and VF221/VF231 have opposite polarities, and the signals are superimposed, but the input noise voltage signals have the same polarity and cancel each other out, realizing the function of noise cancellation. At the same time, the single-ended signal output from the drain of VF301 is directly coupled to the gates of VF302 and VF303, while the signal output from the drain of VF401 is directly coupled to the gates of VF402 and VF403. The current signals output by the drains of VF302 and VF402 are respectively coupled to the sources of VF301 and VF401 through capacitors C ₃₂₁ and C ₄₂₁ , and the sources of VF301 and VF401 are connected to two resistors R ₃₂₁ , One end of R ₄₂₁ is connected. The current signals output by the drains of VF303 and VF403 are respectively connected to the same-named terminals of the primary coils of transformer TF311 and transformer TF411, and their different-named terminals are respectively connected to both ends of the load (Z _L ) via coupling capacitors C3 and C4. That is, after the differential current signals output by the drains of VF303 and VF403 flow through the primary coils of TF311 and TF411 and the coupling capacitors C3 and C4, the differential output current signals (i _O- , i _O+ ) flow into the load Z _L , realizing full The differential power current amplifier amplifies the function of the differential signal. The same-named ends of the secondary coils of TF311 and TF411 are respectively connected to the grids of VF301 and VF401, and the different-named ends are connected to a voltage source U _GG that provides DC bias for the grids.

Table 1 shows the polarity of the signal and noise corresponding to the three nodes X, Y, and Z in Figure 2, showing the process of noise cancellation.

Table 1

In Figure 2, mirror current sources VF304, VF305, VF306, VF307, VF404, VF405, and R ₃₀₂ , R ₃₀₃ , R ₄₀₃ , R ₄₀₂ , and R ₄₀₁ provide bias currents for transistors VF301, VF302, VF303, VF401, VF402, and VF403 .

Claims (4)

1. A fully differential power current amplifier with a noise canceling circuit, comprising a fully differential power current amplifier body, is characterized in that: it also includes a noise canceling circuit, and the noise canceling circuit is composed of two structurally identical canceling branches, Each offset branch consists of cascaded current detection stages, current-voltage conversion stages, voltage-current conversion stages, and mixed current synthesis stages; the signal source is connected to the fully differential power current amplifier body and each offset branch respectively. The input terminal of the current detection stage is connected, the output terminal of the fully differential power current amplifier body is respectively connected to the input terminal of the mixed current synthesis stage of each canceling branch, and the output terminal of the mixed current synthesis stage of each canceling branch is respectively connected to the load ; The fully differential power current amplifier body is composed of two amplifying branches with the same structure, each amplifying branch is correspondingly set with the offsetting branch, and each amplifying branch is composed of Nullor, current parallel negative feedback network, and current series connection A negative feedback network is formed; the current parallel negative feedback network is respectively the first and second transformers (31, 41), and the current series negative feedback network is the first and second resistors (32, 42); the first transformer The end of the same name of the primary coil of (31) is connected with the inverting output end of the first Nullor (30), and the end of the same name of the secondary coil of the first transformer (31) is respectively connected with the non-inverting input end of the first Nullor (30) and the signal Source connection; the opposite end of the primary coil of the first transformer (31) is connected to the input end of the corresponding mixed current synthesis stage, and the opposite end of the secondary coil of the first transformer (31) is grounded; one end of the first resistor (32) Connect the inverting input end and the non-inverting output end of the first Nullor (30); The same name end of the primary coil of the second transformer (41) is connected with the inverting output end of the second Nullor (40), and the second transformer (41 ) of the secondary coil with the same name end connected with the second Nullor (40) in phase input and the signal source; The opposite end of the secondary coil of the two transformers (41) is grounded; one end of the second resistor (42) is connected to the inverting input and the non-inverting output of the second Nullor (40); the first and second resistors (32,42) The other ends are connected to each other. 2. A fully differential power current amplifier with a noise canceling circuit according to claim 1, characterized in that: said current detection stage adopts a current sensor or an integrated transformer. 3. A fully differential power current amplifier with a noise canceling circuit according to claim 1, characterized in that: said mixed current synthesis stage adopts a current adder or subtractor. 4. A fully differential power current amplifier with a noise canceling circuit according to claim 1, characterized in that: said current-voltage conversion stage adopts a passive or active current-voltage conversion circuit.