CN101359232B - Current generating circuit - Google Patents
Current generating circuit Download PDFInfo
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- CN101359232B CN101359232B CN200710075374XA CN200710075374A CN101359232B CN 101359232 B CN101359232 B CN 101359232B CN 200710075374X A CN200710075374X A CN 200710075374XA CN 200710075374 A CN200710075374 A CN 200710075374A CN 101359232 B CN101359232 B CN 101359232B
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Abstract
The invention relates to a current generated circuit which can integrate an over-voltage reducing device; the current is in direct proportion with the temperature (PTAT); the current generated circuit comprises a first cascode current mirror circuit and a second cascode current mirror circuit which are connected between a power supply Vcc and the ground in series; and the current generated circuit also comprises an over- voltage reducing device for restraining the impact ionization effect. The application of the current generated circuit can effectively reduce the drain-source voltage on the cascode device so as to reduce the influence of the impact ionization effect, without affecting the minimum operating voltage; therefore, the current generated circuit keeps the maximum gain of the current mirror structure and fundamentally solves the influence of impact ionization on the cascode, thereby improving the current benchmark linear adjusting rate.
Description
Technical field
The present invention relates to the current reference designing technique, more particularly, relate to the current generating circuit of a kind of be directly proportional with temperature (PTAT) of the line regulation that improves current reference.
Background technology
Voltage reference applies in the mimic channel widely, for example at LDO, and ADC/DAC or the like.It can export a voltage that almost has nothing to do with input voltage and temperature accurately, and the relation of voltage reference and input voltage is weighed with line regulation.Voltage reference with high line regulation provides requisite assurance for the equipment of wide input voltage range.Voltage reference commonly used is based on two kinds of voltage-mode and current-mode.Voltage-mode is utilized two voltages that stability factor is opposite, obtains a voltage that almost has nothing to do with temperature by certain weighting factor addition.Current-mode then is to utilize two electric currents that stability factor is opposite, by certain weighting factor addition obtain one with the almost irrelevant electric current of temperature, flow through a resistance again and obtain a voltage that almost has nothing to do with temperature.
Circuit as shown in Figure 1 often is used to produce the electric current of (PTAT) of being directly proportional with temperature.Yet the variation of input voltage produces error to the mirror image precision of current mirror, makes this PTAT electric current source that produces be very restricted on line regulation.At this problem, cascode structure current mirror as shown in Figure 2 is suggested and is used widely.The cascode structure current mirror makes the output resistance of current mirror increase an intrinsic gain doubly, has improved the mirror image precision of current mirror effectively, has guaranteed its favorable linearity regulation.Yet under the effect of higher power Vcc voltage, the impact ionization effect limits cascode structure maximum gain that can reach, this is because it has introduced one by draining to substrate rather than by the small-signal resistance that drains to the source.The impact ionization effect makes the good linear regulation that showed when operating on low voltage originally worsen.
Summary of the invention
The technical problem to be solved in the present invention is that the above-mentioned defective at prior art provides a kind of current generating circuit.
The technical solution adopted for the present invention to solve the technical problems is: construct a kind of current generating circuit, comprise the overvoltage reducing transformer that the first common-source common-gate current mirror circuit that is connected in series between power Vcc and the ground and the second common-source common-gate current mirror circuit and are used to suppress the impact ionization effect.
In current generating circuit of the present invention, described overvoltage reducing transformer comprises: the first image current device, the second image current device, switching tube and at least two diodes, wherein, first end of the described first image current device first grid end altogether that is connected in that power Vcc, second end are connected with first end of described image current device, control end is connected in the described first common-source common-gate current mirror circuit; Second end of the described second image current device is connected in described control end of switching tube, control end is connected in second of the described first common-source common-gate current mirror circuit and is total to the grid end; First end of described switching tube is connected in first output terminal of the described first common-source common-gate current mirror circuit, the first input end that second end is connected in the described second common-source common-gate current mirror circuit, be connected in series with at least one described diode between first end of described switching tube and second end, be connected in series with at least one described diode between described control end of switching tube and the ground.
In current generating circuit of the present invention, be connected in series with two described diodes between first end of described switching tube and second end.Be connected in series with two described diodes between described control end of switching tube and the ground.
In current generating circuit of the present invention, described first and second image current device is a transistor.Described transistor is N type metal-oxide semiconductor transistor or P type metal-oxide semiconductor transistor.
In current generating circuit of the present invention, described switching tube is transistor or field effect transistor.Described unidirectional conduction device is that diode or triode connects and composes.
The invention has the beneficial effects as follows, can effectively reduce the drain-source voltage that is added on the cascade device, thereby reduce the influence of impact ionization effect, and do not influence minimum operating voltage, the maximum gain of holding current mirror structure, fundamentally solved since impact ionization to the influence of cascade, thereby improved the line regulation of current reference.
Description of drawings
The invention will be further described below in conjunction with drawings and Examples, in the accompanying drawing:
Fig. 1 is the circuit theory diagrams of traditional PTAT current generating circuit;
Fig. 2 is the circuit theory diagrams of the improved-type PTAT current generating circuit of tradition;
Fig. 3 is the circuit theory diagrams of current generating circuit of the present invention;
Fig. 4 is the voltage oscillogram that NodeA among Fig. 3, NodeB and NodeC increase with Vcc.
Embodiment
The big inadequately employed cascode structure of line regulation difference that causes of output resistance that is traditional improvement because of current mirror shown in Figure 2.This structure can not show satisfactory performance under most Vcc is not too high situation.Yet along with the increase of Vcc, the be collided influence of ionisation effect of the N type metal-oxide-semiconductor 100 of voltage stress that bears the overwhelming majority becomes serious gradually.The high-gain of cascode structure is limited, thereby makes the line regulation of PTAT electric current worsen.We know (voltage waveform that NodeB is ordered among Fig. 4 is equal to the voltage waveform that NodeC is ordered among Fig. 2) NodeB waveform from Fig. 4, when Vcc=6V, be added in the voltage difference Vcc-|Vthp| (Vthp is the threshold voltage of pMOSFET) between the 100 drain-source two ends among Fig. 2, greater than 5V.
The improved-type PTAT current generating circuit that the present invention of being shown in Figure 3 proposes, it is integrated overvoltage reducing transformer 201 on the basis of conventional P TAT circuit, makes the voltage difference between the 100 drain-source two ends obtain the pressure drop of certain amplitude, has suppressed the influence of impact ionization effect.It comprises the overvoltage reducing transformer 201 that the first common-source common-gate current mirror circuit 1 that is connected in series between power Vcc and the ground and the second common-source common-gate current mirror circuit 2 and are used to suppress the impact ionization effect.
In the PTAT of integrated overvoltage reducing transformer 201 of the present invention current generating circuit, the first common-source common-gate current mirror circuit 1 comprises: the first transistor 96, transistor seconds 97, the 3rd transistor 98, the 4th transistor 99; Overvoltage reducing transformer 201 comprises: the first image current device 101, the second image current device 102, switching tube 105 and at least two unidirectional conduction devices, wherein, the grid of the first image current device 101 is connected in the grid of the first transistor 96, the drain electrode of the first image current device 101 is connected in power Vcc, the source electrode of the first image current device 101 is connected in the source electrode of the second image current device 102, the grid of the second image current device 102 is connected in the grid of the 3rd transistor 98, the drain electrode of the second image current device 102 is connected in the control end of switching tube 105, first end of switching tube 105 is connected in the drain electrode of the 3rd transistor 98, second end of switching tube 105 is connected in the first input end of the described second common-source common-gate current mirror circuit 2, be connected in series with at least one unidirectional conduction device between first end of switching tube 105 and second end, be connected in series with at least one unidirectional conduction device between the control end of switching tube 105 and the ground.
In current generating circuit of the present invention, be connected in series with two unidirectional conduction devices between first end of switching tube 105 and second end.Be connected in series with two unidirectional conduction devices between the control end of switching tube 105 and the ground.But this unidirectional conduction device diode or connect and compose by triode.
In current generating circuit of the present invention, switching tube 105 is transistor or field effect transistor.
Concrete principle of work is as follows:
As Vcc＜2Vthn, (Vthn is the threshold voltage of nMOSFET 103,104), NodeA approximates Vcc; As Vcc＞=2Vthn, NodeA is about 2Vthn.NodeB is about Vcc-|Vthp|.Conducting situation according to 106,107 can be divided into following two workspaces:
As Vcc≤3|Vthp|, 106,107 is obstructed, and NodeC equals NodeA-Vthn.I2 all flows through from NodeB and 105 arrives NodeC.Voltage difference between the 100 drain-source two ends is NodeA-Vthn at this moment, smaller or equal to Vthn.
As Vcc〉during 3|Vthp|, 106,107 conductings, NodeC equals NodeB-2Vthp.Along with the increase of Vcc, NodeB and then increases, and the voltage of NodeC also and then increases.Gate source voltage reduce increase with substrate bias effect, make 105 to enter by the district very soon.I2 all flows through from NodeB and 106,107 arrives NodeC.Voltage difference between the 100 drain-source two ends is Vcc-3|Vthp| at this moment.
From the above analysis, the overvoltage reducing transformer 201 among the present invention has effectively been expanded the input voltage range that has the good linear regulation.When low supply voltage, I2 all flows through from NodeB and 105 arrives NodeC, and its equivalent electrical circuit is identical with structure shown in Figure 2; When high power supply voltage, 105 is obstructed, I2 all flows through from NodeB and 106,107 arrives NodeC, the drain terminal that its equivalent electrical circuit is equivalent to 100 has been connected in series two unidirectional conduction devices of step-down, make the voltage difference between the 100 drain-source two ends reduce the forward voltage of the unidirectional conduction device of twice, thereby suppressed the influence of impact ionization effectively.The number that it is pointed out that the unidirectional conduction device in two places (103/104 and 106/107) among the present invention can be selected according to the order of severity of the impact ionization effect of the size of practice supply voltage and the MOS that uses.
Claims (8)
1. current generating circuit, comprise the first common-source common-gate current mirror circuit (1) and the second common-source common-gate current mirror circuit (2) that are connected in series between power Vcc and the ground, it is characterized in that, also include an overvoltage reducing transformer (201) that is used to suppress the impact ionization effect; Described overvoltage reducing transformer (201) comprising: the first image current device (101), the second image current device (102), switching tube (105) and at least two unidirectional conduction devices;
The first grid end altogether that first end of the described first image current device (101) is connected in that power Vcc, second end are connected with first end of the described second image current device (102), control end is connected in the described first common-source common-gate current mirror circuit (1);
Control end, the control end that second end of the described second image current device (102) is connected in described switching tube (105) is connected in the second grid end altogether of the described first common-source common-gate current mirror circuit (1);
First end of described switching tube (105) is connected in the first common grid end of the described first common-source common-gate current mirror circuit (1), the first input end that second end is connected in the described second common-source common-gate current mirror circuit (2),
Be connected in series with at least one described unidirectional conduction device between first end of described switching tube (105) and second end,
Be connected in series with at least one described unidirectional conduction device between the control end of described switching tube (105) and the ground.
2. current generating circuit according to claim 1 is characterized in that, is connected in series with two described unidirectional conduction devices (106,107) between first end of described switching tube (105) and second end.
3. current generating circuit according to claim 1 is characterized in that, is connected in series with two described unidirectional conduction devices (103,104) between the control end of described switching tube (105) and the ground.
4. current generating circuit according to claim 1 is characterized in that, the described first image current device (101) and the second image current device (102) are transistors.
5. current generating circuit according to claim 4 is characterized in that, described transistor is a N type metal-oxide semiconductor transistor.
6. current generating circuit according to claim 4 is characterized in that, described transistor is a P type metal-oxide semiconductor transistor.
7. according to the arbitrary described current generating circuit of claim 1～6, it is characterized in that described switching tube (105) is transistor or field effect transistor.
8. according to the arbitrary described current generating circuit of claim 1～6, it is characterized in that described unidirectional conduction device is diode or is connected and composed by triode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200710075374XA CN101359232B (en) | 2007-07-31 | 2007-07-31 | Current generating circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200710075374XA CN101359232B (en) | 2007-07-31 | 2007-07-31 | Current generating circuit |
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| Publication Number | Publication Date |
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| CN101359232A CN101359232A (en) | 2009-02-04 |
| CN101359232B true CN101359232B (en) | 2010-09-08 |
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| CN200710075374XA Active CN101359232B (en) | 2007-07-31 | 2007-07-31 | Current generating circuit |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6924693B1 (en) * | 2002-08-12 | 2005-08-02 | Xilinx, Inc. | Current source self-biasing circuit and method |
| CN1249654C (en) * | 2000-07-26 | 2006-04-05 | Lg电子株式会社 | Electric current control circuit for display equipment |
| CN1908845A (en) * | 2005-08-01 | 2007-02-07 | 义隆电子股份有限公司 | Reference current generation circuit |
-
2007
- 2007-07-31 CN CN200710075374XA patent/CN101359232B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1249654C (en) * | 2000-07-26 | 2006-04-05 | Lg电子株式会社 | Electric current control circuit for display equipment |
| US6924693B1 (en) * | 2002-08-12 | 2005-08-02 | Xilinx, Inc. | Current source self-biasing circuit and method |
| CN1908845A (en) * | 2005-08-01 | 2007-02-07 | 义隆电子股份有限公司 | Reference current generation circuit |
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| Publication number | Publication date |
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| CN101359232A (en) | 2009-02-04 |
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Address after: 518057 room 5-8, 10th floor, Changhong science and technology building, South 12th Road, science and Technology Park, Nanshan District, Shenzhen City, Guangdong Province Patentee after: Huimang Microelectronics (Shenzhen) Co.,Ltd. Address before: 518057 Guangdong city of Shenzhen province science and Technology Park of Nanshan District high SSMEC building four floor Patentee before: FREMONT MICRO DEVICES (SHENZHEN) Ltd. |
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