CN202014234U

CN202014234U - High speed comparator

Info

Publication number: CN202014234U
Application number: CN2011200539023U
Authority: CN
Inventors: 范方平
Original assignee: IPGoal Microelectronics Sichuan Co Ltd
Current assignee: IPGoal Microelectronics Sichuan Co Ltd
Priority date: 2011-03-03
Filing date: 2011-03-03
Publication date: 2011-10-19
Anticipated expiration: 2021-03-03

Abstract

The utility model provides a high speed comparator. The high speed comparator comprises a first switch element, a second switch element, a third switch element, a first resistor connected with the first switch element, a second resistor connected with the second switch element, a third resistor, a fourth resistor and a fifth resistor, wherein, the third resistor is connected between the first switch element and the third switch element; the fourth resistor is connected between the second switch element and the third switch element; and the fifth resistor is connected with the first resistor and the second resistor. The high speed comparator has the advantages that the structure is simple, and the gain cannot be changed along with process changes.

Description

High-speed comparator

Technical field

The utility model relates to a kind of comparator, refers to the high-speed comparator that a kind of gain does not change with technology especially.

Background technology

Along with the development of modern communications technology and signal processing technology, increasing analog signal need change into digital signal and handle, and therefore the analog to digital converter of high-speed, high precision is had higher requirement.But in ultra high-speed adc, the design of high-speed, high precision comparator is the difficult point and the bottleneck of whole design.

The structure of existing high-speed comparator comprises: multistage open loop comparator, latched comparator, dynamic latch comparator and amplify latched comparator in advance.In existing high-speed comparator circuit, its gain tends to change along with the variation of technology, and owing to be subjected to the restriction of amplifier bandwidth, the speed of high-speed comparator is difficult to reach Gsps(megabit of per second).

Summary of the invention

In view of above content, be necessary the high-speed comparator that provides a kind of gain not change with technology.

A kind of high-speed comparator, comprise one first switch element, a second switch element, one the 3rd switch element, first resistance that links to each other with described first switch element, second resistance that links to each other with described second switch element, one the 3rd resistance, one the 4th resistance and one the 5th resistance, described the 3rd resistance is connected between described first switch element and described the 3rd switch element, described the 4th resistance is connected between described second switch element and described the 3rd switch element, and described the 5th resistance links to each other with described first resistance and described second resistance.

Preferably, described first switch element is one first field effect transistor, and described second switch element is one second field effect transistor, and described the 3rd switch element is one the 3rd field effect transistor.

Preferably, the grid of described first field effect transistor connects a first input end, its drain electrode connects an end of one first output and described first resistance, its source class connects an end of described the 3rd resistance, the grid of described second field effect transistor connects one second input, its drain electrode connects an end of one second output and described second resistance, its source class connects an end of described the 4th resistance, described first input end and described second input receive the differential signal of a pair of input, and described first output and described second output are exported a pair of differential signal.

Preferably, the other end of described first resistance and the common end that is connected described the 5th resistance of the other end of described second resistance, the other end of described the 5th resistance connects a power end.

Preferably, the other end of described the 3rd resistance and the common drain electrode that is connected described the 3rd field effect transistor of the other end of described the 4th resistance, the grid of described the 3rd field effect transistor connects a voltage end, and its source class connects an earth terminal.

Relative prior art, the utility model high-speed comparator is simple in structure, and gain does not change with technique change, and is only relevant with the resistors match degree at leakage two ends, field effect transistor source, its bandwidth can be accomplished the GHz level by comparator output resistance and the decision of next stage load capacitance simultaneously.

Description of drawings

Fig. 1 is the circuit diagram of the utility model high-speed comparator better embodiment.

Fig. 2 is the circuit diagram of another execution mode of the utility model high-speed comparator.

Embodiment

See also Fig. 1, the utility model high-speed comparator better embodiment comprises a first input end Vin+, one second input Vin-, one first output end vo ut+, one second output end vo ut-, one first switch element, a second switch element, one the 3rd switch element, one first resistance R 1, one second resistance R 2, one the 3rd resistance R 3, one the 4th resistance R 4 and one the 5th resistance R 5.This first input end Vin+ and this second input Vin-are used to receive a pair of differential signal of input, and this first output end vo ut+ and this second output end vo ut-are used to receive a pair of differential signal of output.

In the present embodiment, this first switch element is one first field effect transistor M1A, and this second switch element is one second field effect transistor M1B, and the 3rd switch element is one the 3rd field effect transistor M3.This first field effect transistor M1A, this second field effect transistor M1B and the 3rd field effect transistor M3 are N type field effect transistor (NMOS).In other embodiments, switch element can change to switch element or the circuit that can realize said function as required.

The annexation of this high-speed comparator better embodiment is: the grid of this first field effect transistor M1A connects this first input end Vin+, its drain electrode connects an end of this first output end vo ut+ and this first resistance R 1, and its source class connects an end of the 3rd resistance R 3.The grid of this second field effect transistor M1B connects this second input Vin-, and its drain electrode connects an end of this second output end vo ut-and this second resistance R 2, and its source class connects an end of the 4th resistance R 4.The other end of this first resistance R 1 and the other end of this second resistance R 2 are connected an end of the 5th resistance R 5 jointly, and the other end of the 5th resistance R 5 connects a power end VDD.The other end of the 3rd resistance R 3 and the other end of the 4th resistance R 4 are connected the drain electrode of the 3rd field effect transistor M3 jointly, and the grid of the 3rd field effect transistor M3 connects a voltage end Vb, and its source class connects an earth terminal VSS.

See also Fig. 2, another execution mode of the utility model high-speed comparator comprises first input end Vin+, the second input Vin-, the first output end vo ut+, the second output end vo ut-, one the 4th switch element, one the 5th switch element, one the 6th switch element, one the 6th resistance R 6, one the 7th resistance R 7, one the 8th resistance R 8, one the 9th resistance R 9 and 1 the tenth resistance R 10.This first input end Vin+ and this second input Vin-are used to receive a pair of differential signal of input, and this first output end vo ut+ and this second output end vo ut-are used to receive a pair of differential signal of output.

In this another execution mode, the 4th switch element is one the 4th field effect transistor M2A, and the 5th switch element is one the 5th field effect transistor M2B, and the 6th switch element is one the 6th field effect transistor M4.The 4th field effect transistor M2A, the 5th field effect transistor M2B and the 6th field effect transistor M4 are P type field effect transistor (PMOS).In other embodiments, switch element can change to switch element or the circuit that can realize said function as required.

The annexation of this another execution mode of high-speed comparator is: the grid of the 4th field effect transistor M2A connects this first input end Vin+, its source class connects an end of the 6th resistance R 3, and its drain electrode connects an end of this first output end vo ut+ and the 8th resistance R 8.The grid of the 5th field effect transistor M2B connects this second input Vin-, and its source class connects an end of the 7th resistance R 7, and its drain electrode connects an end of this second output end vo ut-and the 9th resistance R 9.The other end of the 6th resistance R 6 and the other end of the 7th resistance R 7 are connected the drain electrode of the 6th field effect transistor M4 jointly, and the grid of the 6th field effect transistor M4 connects a voltage end Vbp, and its source class connects power end VDD.The other end of the 8th resistance R 8 and the other end of the 9th resistance R 9 are connected an end of the tenth resistance R 10 jointly, and the other end of the tenth resistance R 10 connects earth terminal VSS.

Circuit with Fig. 1 is an example, and the principle Analysis of this high-speed comparator better embodiment is as follows:

1. gain is derived

In the present embodiment, suppose R1=R2=Rd, R3=R4=Rs, the first field effect transistor M1A, the second field effect transistor M1B are input pipe, and this high-speed comparator is carried out monolateral equivalence, can obtain its gain formula and be:

Vout/Vin=-gm·ro·Rd/(Rd+Rs+ro·(1+(gm+gmb)·Rs))

Wherein Vout represents output voltage, and Vin represents input voltage, and gm represents the mutual conductance of the first field effect transistor M1A, and gmb represents the mutual conductance of the second field effect transistor M1B, and ro represents the small-signal output resistance.By suitable biasing, make (gm+gmb) Rsro " Rd, Rs, ro, then gain formula can be reduced to

Vout/Vin=-Rd/ ((1+ η) Rs), wherein η=gmb/gm

Can be got by following formula, the gain of this high-speed comparator is only relevant with Rd, Rs, gmb/gm, if do not consider to serve as a contrast inclined to one side effect, i.e. and metal-oxide-semiconductor source end and substrate short circuit, then gain formula can be changed into:

Vout/Vin=-Rd/Rs

We can mate Rd, Rs in domain accurately, and then its gain is just no longer with the technology conversion, and also irrelevant with bias current.

2. bandwidth analysis

Suppose that the output limit is Pout, make that load capacitance is Cout, then

Pout=1/(Rd·Cout)

Generally speaking, Rd is 5 ~ 10kohm(kilohm), Cout multiply by 10 negative 15 powers for the 50fF(farad), Pout=2 ~ 4GHz(Gigahertz then).

3. cascade

This structure one pass gain is not high, can possess filter effect simultaneously by cascade to obtain high-gain.

The utility model high-speed comparator is simple in structure, and gain does not change with technique change, and only relevant with the resistors match degree at leakage two ends, field effect transistor source, its bandwidth can be accomplished the GHz level by comparator output resistance and the decision of next stage load capacitance simultaneously.

Claims

1. high-speed comparator, it is characterized in that: described high-speed comparator comprises one first switch element, one second switch element, one the 3rd switch element, one first resistance that links to each other with described first switch element, one second resistance that links to each other with described second switch element, one the 3rd resistance, one the 4th resistance and one the 5th resistance, described the 3rd resistance is connected between described first switch element and described the 3rd switch element, described the 4th resistance is connected between described second switch element and described the 3rd switch element, and described the 5th resistance links to each other with described first resistance and described second resistance.

2. high-speed comparator as claimed in claim 1 is characterized in that: described first switch element is one first field effect transistor, and described second switch element is one second field effect transistor, and described the 3rd switch element is one the 3rd field effect transistor.

3. high-speed comparator as claimed in claim 2, it is characterized in that: the grid of described first field effect transistor connects a first input end, its drain electrode connects an end of one first output and described first resistance, its source class connects an end of described the 3rd resistance, the grid of described second field effect transistor connects one second input, its drain electrode connects an end of one second output and described second resistance, its source class connects an end of described the 4th resistance, described first input end and described second input receive the differential signal of a pair of input, and described first output and described second output are exported a pair of differential signal.

4. high-speed comparator as claimed in claim 3 is characterized in that: the other end of described first resistance and the common end that is connected described the 5th resistance of the other end of described second resistance, the other end of described the 5th resistance connects a power end.

5. high-speed comparator as claimed in claim 4, it is characterized in that: the other end of described the 3rd resistance and the common drain electrode that is connected described the 3rd field effect transistor of the other end of described the 4th resistance, the grid of described the 3rd field effect transistor connects a voltage end, and its source class connects an earth terminal.