Summary of the invention
In view of this, the invention provides a kind of self-bias current source, to reduce in the existing self-bias current source because the impact that start-up circuit causes self-bias current source in the process that starts and turn-off.
For achieving the above object, the invention provides following technical scheme:
A kind of self-bias current source comprises:
Current source module is for generation of output current;
Current mirror module links to each other with described current mirror module, for generation of the input current that equates with described output current;
The start-up circuit module links to each other with current mirror module, and is connected with described current source module by the second resistance, is used to described current source module and current mirror module that starting current is provided.
Preferably, current source module comprises:
The first triode of base stage and the equal ground connection of collector and the second triode;
One end connects the first resistance of described the second transistor emitter;
Source electrode connects the first field effect transistor of described the first transistor emitter, and the grid of described the first field effect transistor links to each other with drain electrode;
Grid connects the grid of described the first field effect transistor, and source electrode connects the second field effect transistor of the other end of described the first resistance.
Preferably, current mirror module comprises:
Drain electrode connects the drain electrode of described the first field effect transistor, and source electrode connects the 3rd field effect transistor of power supply;
Drain electrode connects the drain electrode of described the second field effect transistor, and grid connects the grid of described the 3rd field effect transistor, and source electrode connects the 4th field effect transistor of power supply, the grid of described the 4th field effect transistor and the connection that is connected.
Preferably, the start-up circuit module comprises:
Source electrode connects power supply, and grid connects the 5th field effect transistor of the grid of described the 4th field effect transistor;
Source electrode connects power supply, the 6th field effect transistor of grounded-grid;
Drain electrode connects the drain electrode of described the 6th field effect transistor, the 7th field effect transistor of source ground;
Drain electrode connects the drain electrode of described the 5th field effect transistor, and grid connects the grid of described the 7th field effect transistor, the 8th field effect transistor of source ground, and the grid of described the 8th field effect transistor is connected with drain electrode;
Drain electrode connects the drain electrode of described the second field effect transistor, and grid connects the 9th field effect transistor of the drain electrode of described the 7th field effect transistor;
One end connects the source electrode of described the 9th field effect transistor, the second resistance of other end ground connection;
Wherein, described the second resistance is used for by limiting the voltage of described the 9th field effect transistor, turn-offing described the 9th field effect transistor after described self-bias current source starts.
Preferably, described the first field effect transistor and described the second field effect transistor are same field effect transistor.
Via above-mentioned technical scheme as can be known, compared with prior art, the invention discloses a kind of self-bias current source.This self-bias current source is comprised of current source module, current mirror module and start-up circuit module.In the start-up circuit module of this self-bias current source, increased by the second resistance.Increase after this second resistance, after self-bias current source started, the second resistance can make the more reliable shutoff of start-up circuit module, can reduce the start-up circuit module to the impact of self-bias current source.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the invention, the technical scheme in the embodiment of the invention is clearly and completely described, obviously, described embodiment only is the present invention's part embodiment, rather than whole embodiment.Based on the embodiment among the present invention, those of ordinary skills belong to the scope of protection of the invention not making the every other embodiment that obtains under the creative work prerequisite.
By background technology as can be known, the start-up circuit of self-bias current source commonly used breaks away from the process of zero current condition self-bias current source, because field effect transistor is in the process of conducting and shutoff, grid voltage changes greatly, can cause its drain current to produce larger variation, and, because the impact of subthreshold value conducting effect, field effect transistor is difficult to turn-off fully, will directly cause start-up circuit in the process that starts and turn-off self-bias current source to be impacted.
The invention discloses a kind of self-bias current source.This self-bias current source is comprised of current source module, current mirror module and start-up circuit module.In the start-up circuit module of this self-bias current source, increased by the second resistance.Increase after this second resistance, after self-bias current source started, the second resistance can make the more reliable shutoff of start-up circuit module, can reduce start-up circuit to the impact of self-bias current source.
Circuit structure and principle relevant for above-mentioned self-bias current source will be described in detail by following examples.
Embodiment one
See also accompanying drawing 2, be the structural representation of the embodiment of the invention one disclosed a kind of self-bias current source.This self-bias current source specifically comprises:
Current source module 10 is for generation of output current;
Current mirror module 11 links to each other with described current mirror module 10, for generation of the input current that equates with described output current;
Start-up circuit module 12 links to each other with current mirror module 10, and is connected with described current source module 11 by the second resistance, is used to described current source module 10 and current mirror module 11 that starting current is provided.
In the present embodiment, self-bias current source is comprised of current source module, current mirror module and start-up circuit module.In the start-up circuit module of this self-bias current source, increased by the second resistance.Increase after this second resistance, after self-bias current source started, the second resistance can make the more reliable shutoff of start-up circuit module, can reduce the start-up circuit module to the impact of self-bias current source.
Embodiment two
See also accompanying drawing 3, be the electrical block diagram of the embodiment of the invention two disclosed another kind of self-bias current source.This self-bias current source specifically comprises:
The first triode Q of base stage and the equal ground connection of collector
1With the second triode Q
2
One end connects described the second triode Q
2The first resistance R of emitter;
Source electrode connects described the first triode Q
1The first field effect transistor M of emitter
1, described the first field effect transistor M
1Grid with the drain electrode link to each other;
Grid connects described the first field effect transistor M
1Grid, source electrode connects the second field effect transistor M of the other end of described the first resistance R
2
Drain electrode connects described the first field effect transistor M
1Drain electrode, source electrode connects power supply V
DDThe 3rd field effect transistor M
3
Drain electrode connects described the second field effect transistor M
2Drain electrode, grid connects described the 3rd field effect transistor M
3Grid, source electrode connects power supply V
DDThe 4th field effect transistor M
4, described the 4th field effect transistor M
4Grid and the connection that is connected;
Source electrode connects power supply V
DD, grid connects described the 4th field effect transistor M
4The 5th field effect transistor M of grid
5
Source electrode connects power supply V
DD, the 6th field effect transistor M of grounded-grid
6
Drain electrode connects described the 6th field effect transistor M
6Drain electrode, the 7th field effect transistor M of source ground
7
Drain electrode connects described the 5th field effect transistor M
5Drain electrode, grid connects described the 7th field effect transistor M
7Grid, the 8th field effect transistor M of source ground
8, described the 8th field effect transistor M
8Grid with the drain electrode be connected;
Drain electrode connects described the second field effect transistor M
2Drain electrode, grid connects described the 7th field effect transistor M
7The 9th field effect transistor M of drain electrode
9
One end connects described the 9th field effect transistor M
9Source electrode, the second resistance R of other end ground connection
S
Wherein, described the second resistance R
SBe used for after described self-bias current source starts, by limiting described the 9th field effect transistor M
9Voltage, turn-off described the 9th field effect transistor M
9
Based on above-mentioned annexation, the principle of work of this self-bias current source is specific as follows:
The first field effect transistor M
1, the second field effect transistor M
2, the first triode Q
1, the second triode Q
2And first resistance R jointly form current source module, produce output current I
OUTThe 3rd field effect transistor M
3And the 4th field effect transistor M
4Form current mirror module, current mirror gain is 1, makes I
IN=I
OUTThe first field effect transistor M
1With the second field effect transistor M
2Be same field effect transistor, and generally be large-sized transistor that its gate source voltage equates, can obtain:
Then,
If Q
2With Q
1The ratio of launch site area be n:1, can obtain
Wherein, V
TBe thermal voltage.
The temperature coefficient of this self-bias current source is lower, and temperature characterisitic is relatively better.
The 5th field effect transistor M
5, the 6th field effect transistor M
6, the 7th field effect transistor M
7, the 8th field effect transistor M
8, the 9th field effect transistor M
9And second resistance R
SConsist of the start-up circuit module of self-bias current source, wherein R
SBe positioned at the 9th field effect transistor M
9Source electrode and ground between.
When self-bias current source is in zero current condition, the 6th field effect transistor M
6Conducting is to the 9th field effect transistor M
9Gate charges so that the 9th field effect transistor M
9Conducting, thus dragged down the 3rd field effect transistor M
3, the 4th field effect transistor M
4And the 5th field effect transistor M
5Grid voltage, have electric current to flow through in the self-bias current source, broken away from zero current condition.The 8th field effect transistor M
8The 5th field effect transistor M that flows through
5With the 8th field effect transistor M
8Current mirror to the seven field effect transistor M
7, the 6th field effect transistor M
6With the 7th field effect transistor M
7During simultaneously conducting, by choosing rational device size, can make the 6th field effect transistor M
6With the 7th field effect transistor M
7Drain voltage, that is the 9th field effect transistor M
9Grid voltage very low, until the 9th field effect transistor M
9Turn-off.Because the second resistance R
SExistence, for same grid voltage, the 9th field effect transistor M
9Gate source voltage diminish, this can make the 9th field effect transistor M
9More reliable shutoff.
The second resistance R
SAlso can make the 9th field effect transistor M
9Source potential be higher than its body terminal potential, cause the substrate mudulation effect, so that the 9th field effect transistor M
9Threshold voltage become large, further guaranteed the 9th field effect transistor M
9More reliable shutoff has reduced the impact of start-up circuit on self-bias current source.
The process of self-bias current source from zero current condition to the normal operating conditions transition, the 9th field effect transistor M
9Grid voltage experienced larger variation, the second resistance R
SPlay local degenerative effect, reduced the 9th field effect transistor M
9The variation of drain current, thus the impact of start-up circuit on self-bias current source reduced.
Need to prove the second resistance R
2Resistance value do not have specific scope, can be according to the resistance of the different resistances of circuit actual conditions choice for use.
The disclosed self-bias current source of the embodiment of the invention is at the start-up circuit of this self-bias current source, at the 9th field effect transistor M
9Source electrode and ground between increased by the second resistance R
SIncrease this second resistance R
SAfter, after self-bias current source starts, the second resistance R
SCan make the 9th field effect transistor M
9Gate source voltage diminish, and can make the 9th field effect M
9It is large that the threshold voltage of pipe becomes, and guarantees its more reliable shutoff; And, at the 9th field effect transistor M
9In the process of conducting and shutoff, this second resistance R
SCan play the effect of LOCAL FEEDBACK, reduce the 9th field effect transistor M
9The variation of drain current.The 9th field effect transistor M
9Reliable turn-off and the less variation of drain current, all can reduce start-up circuit to the impact of self-bias current source.
In sum:
The invention discloses a kind of self-bias current source.At the start-up circuit of this self-bias current source, between the source electrode of the 9th field effect transistor and ground, increased by the second resistance.Increase after this second resistance, after self-bias current source started, the second resistance can make the gate source voltage of the 9th field effect transistor diminish, and can make the threshold voltage of the 9th field effect transistor become large, guaranteed its more reliable shutoff; And in the process of the 9th field effect transistor conducting and shutoff, this second resistance can play the effect of LOCAL FEEDBACK, reduces the variation of the 9th field effect transistor drain current.
The present invention is by the method for the start-up circuit of improvement self-bias current source, after the self-bias current source disengaged position, guaranteed the more reliable shutoff of start-up circuit, and in the process of self-bias current source duty conversion, reduce the variation of start-up circuit working current, thereby reduced the impact of start-up circuit on self-bias current source.
Each embodiment adopts the mode of going forward one by one to describe in this instructions, and what each embodiment stressed is and the difference of other embodiment that identical similar part is mutually referring to getting final product between each embodiment.
To the above-mentioned explanation of the disclosed embodiments, make this area professional and technical personnel can realize or use the present invention.Multiple modification to these embodiment will be apparent concerning those skilled in the art, and General Principle as defined herein can in the situation that does not break away from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention will can not be restricted to these embodiment shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.