CN102495655A - Threshold voltage generation circuit and method - Google Patents

Abstract

The invention discloses a threshold voltage generation circuit. The threshold voltage generation circuit comprises a first switch element, a second switch element connected with the first switch element, a third switch element connected with the second switch element, a current source connected with the third switch element, a power terminal connected with the current source, an earthing terminal connected with the first switch element and an output terminal connected with the first and second switch elements to output the threshold voltage. The width to length ratio of the first switch element is equal to the width to length ratio of the third switch element and is three times of the width to length ratio of the second switch element. The invention further provides a threshold voltage generation method. The threshold voltage generation circuit can generate accurate threshold voltage and is simple in structure and easy to realize.

Description

Threshold voltage produces circuit and method

Technical field

The present invention relates to a kind of voltage generation circuit and method, refer to that especially a kind of threshold voltage that can produce threshold voltage produces circuit and method.

Background technology

Usually the corresponding input voltage of terminal point that output voltage in the transfer curve is changed with input voltage and sharply change the break over region is called threshold voltage, is also referred to as cut-in voltage.

Threshold voltage can be followed the variation of flow-route and temperature usually and changed, and in the prior art, often obtains threshold voltage through searching database, and process is very complicated, and spended time is longer, and efficient is very low.Therefore, be necessary to provide a kind of simple in structure and threshold voltage that can directly produce more accurate threshold voltage to produce circuit and method.

Summary of the invention

In view of above content, be necessary to provide a kind of threshold voltage that can produce threshold voltage to produce circuit and method.

A kind of threshold voltage produces circuit; Said threshold voltage produces earth terminal and that power end, that current source, that the 3rd on-off element, that second switch element, that circuit comprises that one first on-off element, links to each other with said first on-off element links to each other with said second switch element links to each other with said the 3rd on-off element links to each other with said current source links to each other with said first on-off element and links to each other with said first on-off element and said second switch element and be used to export the output terminal of a threshold voltage; The breadth length ratio of said first on-off element equates with the breadth length ratio of said the 3rd on-off element, and is three times of breadth length ratio of said second switch element.

A kind of threshold voltage production method may further comprise the steps:

One first FET, one second FET, one the 3rd FET and a current source are provided, and the breadth length ratio of said first FET equates with the breadth length ratio of said the 3rd FET, and is three times of breadth length ratio of said second FET;

The grid of said first FET and the drain electrode of said second FET and the source class of said the 3rd FET are linked together;

The grid of the grid of said second FET, said the 3rd FET and an end of drain electrode and said current source are linked together;

The other end and a power end of said current source are linked together;

The source class and an earth terminal of said first FET are linked together;

The drain electrode of said first FET and the source class of said second FET are connected to an output terminal jointly; And

Said output terminal is exported the threshold voltage of a FET.

Relative prior art; Threshold voltage of the present invention produces circuit and method can follow the threshold voltage that the variation of flow-route and temperature produces a more accurate FET; And circuit structure is simple; Only need to adopt three FETs and current source just can realize the output of threshold voltage, do not have any mirror image error, be easy to realize.

Description of drawings

Fig. 1 produces the system architecture diagram of circuit preferred embodiments for threshold voltage of the present invention.

Fig. 2 is the process flow diagram of threshold voltage production method preferred embodiments of the present invention.

Embodiment

See also Fig. 1, threshold voltage of the present invention produces the output terminal VOUT that earth terminal GND and that power end VDD, that current source I, that the 3rd on-off element, that second switch element, that the circuit preferred embodiments comprises that one first on-off element, links to each other with this first on-off element links to each other with this second switch element links to each other with the 3rd on-off element links to each other with this current source I links to each other with this first on-off element links to each other with this first on-off element and this second switch element.

In this embodiment, this first on-off element is one first FET M1, and this second switch element is one second FET M2, and the 3rd on-off element is one the 3rd FET M3.And this first FET M1, this second FET M2 and the 3rd FET M3 are N type FET (NMOS).In other embodiments, on-off element can change to other on-off element or the circuit that can realize said function as required.

The annexation that threshold voltage of the present invention produces the circuit preferred embodiments is following: the grid of this first FET M1 links to each other with the drain electrode of this second FET M2 and the source class of the 3rd FET M3; The source class of this first FET M1 links to each other with this earth terminal GND, and the drain electrode of this first FET M1 is connected this output terminal VOUT jointly with the source class of this second FET M2.The grid of this second FET M2, the grid of the 3rd FET M3 and the common end that is connected this current source I of drain electrode.The other end of this current source I links to each other with this power end VDD.

Threshold voltage of the present invention produces the circuit preferred embodiments can follow the threshold voltage VTH that the variation of flow-route and temperature produces a more accurate FET, and concrete principle Analysis is following:

This first FET M1 and the 3rd FET M3 work in the saturation region; This second FET M2 works in linear zone; The breadth length ratio of supposing this first FET M1 is (W/L)

; The breadth length ratio of this second FET M2 is (W/L)

, and the breadth length ratio of the 3rd FET M3 is (W/L)

.Then produce circuit and can calculate first voltage V1 shown in publishing picture and the value of the second voltage V2 respectively by this threshold voltage:

V1＝VTH+2I/(μn?*Cox*(W/L)

)

；

V2＝V1+VTH+2I/(μn?*Cox*(W/L)

)

；

Because this second FET M2 works in linear zone, then can obtain:

I/(μn?*Cox*(W/L)

)=(V2-VOUT-VTH)(V1-VOUT)-0.5*(V1-VOUT) ；

Bring the expression formula of V1 and V2 into following formula, can get:

I/(μn?*Cox*(W/L)

)＝(VTH-VOUT+2I/(μn?*Cox*(W/L)

) +2I/(μn?*Cox*(W/L)

) )(VTH-VOUT+2I/(μn?*Cox*(W/L)

)

)

-0.5*(?VTH-VOUT+2I/(μn?*Cox*(W/L)

) )

；

Can get by following formula; If make VTH=VOUT; (W/L)

=(W/L)

=W/L, then following formula can get by abbreviation:

I/(μn?*Cox*(W/L) )＝4I/(μn?*Cox*(W/L))－I/(μn?*Cox*(W/L))＝3I/(μn?*Cox*(W/L))；

That is: 3* (W/L)

=W/L; Wherein μ n represents electron mobility, and Cox represents the gate oxide unit-area capacitance.

This shows; Only need to be provided with (W/L)

=(W/L)

=3* (W/L)

; The breadth length ratio that the first FET M1 promptly is set equates with the breadth length ratio of the 3rd FET M3; And be three times of breadth length ratio of the second FET M2; Just can make VOUT=VTH, i.e. the voltage of output terminal VOUT output is the threshold voltage VTH of FET.

See also Fig. 2, the variation that threshold voltage production method preferred embodiments of the present invention can be followed flow-route and temperature produces the threshold voltage VTH of a more accurate FET, and this threshold voltage production method may further comprise the steps:

Step 1 provides three FET M1, M2, M3 and current source I, and the breadth length ratio of the first FET M1 equates with the breadth length ratio of the 3rd FET M3, and is three times of breadth length ratio of the second FET M2.

Step 2 links together the grid of the first FET M1 and the drain electrode of second FET and the source class of the 3rd FET.

Step 3 links together the grid of the second FET M2, the grid of the 3rd FET M3 and the end of drain electrode and current source I.

Step 4 links together the other end and the power end VDD of current source I.

Step 5 links together source class and the earth terminal GND of the first FET M1.

Step 6 is connected to output terminal VOUT jointly with the drain electrode of the first FET M1 and the source class of the second FET M2.

Step 7, the threshold voltage VTH of the FET that output terminal VOUT output is more accurate.

Threshold voltage of the present invention produces circuit and method can follow the threshold voltage that the variation of flow-route and temperature produces a more accurate FET; And circuit structure is simple; Only need to adopt three FETs and current source just can realize the output of threshold voltage; There is not any mirror image error, is easy to realize.

Claims (8)

1. a threshold voltage produces circuit; It is characterized in that: said threshold voltage produces earth terminal and that power end, that current source, that the 3rd on-off element, that second switch element, that circuit comprises that one first on-off element, links to each other with said first on-off element links to each other with said second switch element links to each other with said the 3rd on-off element links to each other with said current source links to each other with said first on-off element and links to each other with said first on-off element and said second switch element and be used to export the output terminal of a threshold voltage; The breadth length ratio of said first on-off element equates with the breadth length ratio of said the 3rd on-off element, and is three times of breadth length ratio of said second switch element.

2. threshold voltage as claimed in claim 1 produces circuit; It is characterized in that: said first on-off element is one first FET; Said second switch element is one second FET; Said the 3rd on-off element is one the 3rd FET, and said first FET, said second FET and said the 3rd FET are N type FET.

3. threshold voltage as claimed in claim 2 produces circuit, and it is characterized in that: the grid of said first FET links to each other with the drain electrode of said second FET and the source class of said the 3rd FET.

4. threshold voltage as claimed in claim 3 produces circuit, and it is characterized in that: the source class of said first FET links to each other with said earth terminal.

5. threshold voltage as claimed in claim 4 produces circuit, it is characterized in that: the drain electrode of said first FET is connected said output terminal jointly with the source class of said second FET.

6. threshold voltage as claimed in claim 5 produces circuit; It is characterized in that: the grid of the grid of said second FET, said the 3rd FET and the common end that is connected said current source of drain electrode, the other end of said current source links to each other with said power end.

7. threshold voltage production method may further comprise the steps:

One first FET, one second FET, one the 3rd FET and a current source are provided, and the breadth length ratio of said first FET equates with the breadth length ratio of said the 3rd FET, and is three times of breadth length ratio of said second FET;

The grid of said first FET and the drain electrode of said second FET and the source class of said the 3rd FET are linked together;

The grid of the grid of said second FET, said the 3rd FET and an end of drain electrode and said current source are linked together;

The other end and a power end of said current source are linked together;

The source class and an earth terminal of said first FET are linked together;

The drain electrode of said first FET and the source class of said second FET are connected to an output terminal jointly; And

Said output terminal is exported the threshold voltage of a FET.

8. threshold voltage production method as claimed in claim 7 is characterized in that: said first FET, said second FET and said the 3rd FET are N type FET.

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