CN205265629U - Feedforward is bars transimpedance amplifier circuit altogether with active inductance structure - Google Patents

Abstract

The utility model discloses a feedforward is bars transimpedance amplifier circuit altogether with active inductance structure, be total to bars transimpedance amplifier circuit and active inductive circuit including the feedforward, the feedforward altogether output of bars transimpedance amplifier circuit is established ties behind pull -up resistance R1 and the active inductive circuit in proper order, connects the voltage source, feedforward bars transimpedance amplifier circuit altogether includes input power, NMOS transistor M1, NMOS transistor M2, NMOS transistor M3 and NMOS transistor M4. The utility model discloses a be the structure of active inductance, has alleviated and has striden the restriction relation that hinders between gain and the bandwidth, can obtain bigger striding and hinder the gain in the same work bandwidth, because what adopt is active inductance to do not increase the area of domain.

Description

There is the feedforward grid trans-impedance amplifier circuit altogether of active inductance structure

Technical field:

The utility model relates to Analogous Integrated Electronic Circuits, relates in particular to the technology of fiber optic communication field trans-impedance amplifier.

Background technology:

Low area in Optical Receivers, low cost, high bandwidth, the trans-impedance amplifier of high transimpedance gain is thereinPlay the part of an important role.

Recent years, the trans-impedance amplifier of feedforward common gate structure is because overcome the RGC (Regulated adoptingCascode) the intrinsic large shortcoming of voltage margin consumption of structure, has realized high bandwidth, high-gain, low noiseThe design of pre-amplification circuit. But can there is certain restricting relation, Wu Fa between transimpedance gain and bandwidthIn the impregnable situation of bandwidth, the transimpedance gain of raising.

Utility model content

The technical problems to be solved in the utility model is: the trans-impedance amplifier of existing feedforward common gate structure cannot beIn the impregnable situation of bandwidth, the transimpedance gain of raising.

For addressing the above problem, the technical solution adopted in the utility model is: have the feedforward of active inductance structureGrid trans-impedance amplifier circuit altogether, comprises feedforward grid trans-impedance amplifier circuit and active inductance circuit altogether; Described feedforwardThe output of grid trans-impedance amplifier circuit is connected after pull-up resistor R1 and active inductance circuit successively altogether, connects electricityVoltage source; Described feedforward altogether grid trans-impedance amplifier circuit comprises input power, nmos pass transistor M1, NMOSTransistor M2, nmos pass transistor M3 and nmos pass transistor M4; Input power comprises current source in parallelAnd electric capacity, its output connects respectively the source electrode of nmos pass transistor M1 and nmos pass transistor M2, andThe drain electrode of nmos pass transistor M4; The source electrode of nmos pass transistor M1 and nmos pass transistor M2 is signalInput, the drain electrode of nmos pass transistor M1 connects pull-up resistor R1, and the drain electrode of nmos pass transistor M2 connectsConnecting and draw resistance R 2, is the biasing of nmos pass transistor M3 grid; The drain electrode of nmos pass transistor M3 connectsPull-up resistor R3 is the biasing of nmos pass transistor M1 grid; The source ground of nmos pass transistor M4,The grid of the grid of nmos pass transistor M4 and nmos pass transistor M2 is all connected voltage source Vb; On draw electricityResistance R2 is all connected supply voltage VDD2 with pull-up resistor R3; Described active inductance circuit comprises resistance R 4 HesNmos pass transistor M5, the grid contact resistance R4 of nmos pass transistor M5, source electrode connects pull-up resistor R1,Drain electrode connects supply voltage VDD1.

Advantage of the present utility model: what the utility model adopted is the structure of active inductance, has alleviated transimpedance gainAnd the restricting relation between bandwidth. In identical bandwidth of operation, can obtain larger transimpedance gain. BecauseWhat adopt is active inductance, does not increase the area of domain.

Brief description of the drawings

Fig. 1 is existing FCG trans-impedance amplifier circuit diagram.

Fig. 2 is the utility model circuit diagram.

Fig. 3 is the equivalent model of the utility model active inductance.

Detailed description of the invention

As shown in Figure 1, the small-signal equivalent circuit of existing FCG trans-impedance amplifier, the transmission letter of its transimpedance gainNumber is as follows:

$Z_{T/FCG}\≈\frac{R_1\·g_{m1}(1+(g_{m2}+g_{mb2}\left)R_2{g}_{m3}{R}_3\right)+R_1\·g_{mb1}}{g_{m1}(1+(g_{m2}+g_{mb2}\left)R_2{g}_{m3}{R}_3\right)+(g_{m2}+g_{mb2}+g_{mb1}+g_{ds4})}\≈R_1$

Can draw from formula, the way that improves transimpedance gain is exactly mainly to improve the resistance of M1 drain electrode. ButIncrease drain resistance R1 and can cause the change of dominant pole, when the limit of output approach input limit timeWait, bandwidth will be greatly affected.

As Figure 2-3, the feedforward that has an active inductance structure altogether grid trans-impedance amplifier comprises five NMOS crystalline substancesBody pipe M1, M2, M3, M4, M5, wherein M1 (M2) source electrode is the input of signal, the drain electrode of M3With drain electrode contact resistance R3 and the R2 respectively of M2, the drain electrode of M1 connects having of R1 and M5 and R4 compositionSource inductance, and the simultaneously drain electrode of M2 and the drain electrode of M3 are respectively as the biasing of M3 and M1 grid. Power supplyVoltage V_DD1Size be 2.5V, V_DD2Size be 1.8V, V_bSize be 0.9V, can be by additionalDC offset voltage, or band-gap reference power supply provides, and repeats no more here. The structure of active inductance is as Fig. 3Shown in, equivalent inductance looks that from Vin the size of L is:

$L\≈\frac{R_4{C}_{gs5}}{g_{m5}}$

The series connection of equivalent inductance and resistance equals to have formed shunt peaking, can, the in the situation that of large resistance, keepBandwidth constant.

The utility model, in the situation that not changing bandwidth, has introduced that active inductance is in series with a resistor to be leaked as M1The structure of utmost point load. The drain electrode load of M1 can be equivalent to a larger resistance series inductance, is obtaining moreWhen large transimpedance gain, the series inductance of equivalence has suppressed the impact of output limit for whole bandwidth simultaneously.

Claims (1)

1. the feedforward grid trans-impedance amplifier circuit altogether with active inductance structure, is characterized in that: comprise feedforward grid altogetherTrans-impedance amplifier circuit and active inductance circuit;

Described feedforward is connect successively pull-up resistor R1 and active inductance of the output of grid trans-impedance amplifier circuit altogetherAfter circuit, connect voltage source;

Described feedforward altogether grid trans-impedance amplifier circuit comprises input power, nmos pass transistor M1, NMOS crystalline substanceBody pipe M2, nmos pass transistor M3 and nmos pass transistor M4;

Input power comprises current source in parallel and electric capacity, and its output connects respectively nmos pass transistor M1With the source electrode of nmos pass transistor M2, and the drain electrode of nmos pass transistor M4;

The source electrode of nmos pass transistor M1 and nmos pass transistor M2 is signal input part, NMOS crystalThe drain electrode of pipe M1 connects pull-up resistor R1,

The drain electrode of nmos pass transistor M2 connects pull-up resistor R2, for nmos pass transistor M3 grid partiallyPut;

The drain electrode of nmos pass transistor M3 connects pull-up resistor R3, for nmos pass transistor M1 grid partiallyPut;

The source ground of nmos pass transistor M4, the grid of nmos pass transistor M4 and nmos pass transistorThe grid of M2 all connects voltage source Vb;

Pull-up resistor R2 is all connected supply voltage V with pull-up resistor R3_DD2；

Described active inductance circuit comprises resistance R 4 and nmos pass transistor M5, nmos pass transistor M5'sGrid contact resistance R4, source electrode connects pull-up resistor R1, and drain electrode connects supply voltage V_DD1。