一种恒流源电路结构 本申请要求在 2011年 12月 29日提交中国专利局、 申请号为 201110450161.7、 发明名称 为 "一种恒流源电路结构" 的中国专利申请的优先权， 其全部内容通过引用结合在本申请 中。 The present invention claims the priority of the Chinese patent application filed on Dec. 29, 2011, the Chinese Patent Application No. 201110450161.7, entitled "A Constant Current Source Circuit Structure", the entire contents of which is incorporated herein by reference. This is incorporated herein by reference.
技术领域Technical field
本发明涉及电路结构， 本发明尤其涉及一种 IC恒流源的电路结构。 背景技术 The present invention relates to a circuit structure, and more particularly to a circuit structure of an IC constant current source. Background technique
恒流源电路是一种输出电流保持恒定的电路。 理想的恒流源电路应当具 有输出电流不会随负载输出电压的变化而变、 不因环境温度变化而变以及内 阻无限大从而电流全部流出到外面的特性。 A constant current source circuit is a circuit in which the output current is kept constant. The ideal constant current source circuit should have the characteristics that the output current does not change with the load output voltage, does not change due to changes in the ambient temperature, and the internal resistance is infinite, so that the current flows out to the outside.
为了使恒流源电路具有上述特性， 必须使恒流源电路的输出级具有饱和 的输出电流伏安特性。 为此， 通常要求恒流源电路的输入电压保持稳定， 也 即要求输入级必须是恒压源； 而输出电阻尽量大，也即要求输出级是恒流源。 In order for the constant current source circuit to have the above characteristics, the output stage of the constant current source circuit must have a saturated output current volt-ampere characteristic. For this reason, the input voltage of the constant current source circuit is usually required to be stable, that is, the input stage must be a constant voltage source; and the output resistance is as large as possible, that is, the output stage is required to be a constant current source.
通常情况下， 将三极管适当连接成集成二极管的形式， 使其具有指数形 式的伏安特性或是抛物线形式上升的伏安特性。 Typically, the triodes are suitably connected in the form of an integrated diode that has an exponential volt-ampere characteristic or a parabolic volt-ampere characteristic.
图 la和图 lb示出了两种基本形式的恒流源电路。其中， 图 la釆用的是双极 结晶体管结构， 而图 lb采用的是金属氧化物场效应晶体管结构。 Figures la and lb show two basic forms of constant current source circuits. Among them, Fig. la釆 uses a bipolar junction transistor structure, and Figure lb uses a metal oxide field effect transistor structure.
图 la和 lb所示的恒流源电路具有如图 2所示的输入 -输出伏安特性。 The constant current source circuit shown in Figures la and lb has an input-output volt-ampere characteristic as shown in Fig. 2.
从图 2可以看出， 图 la和图 lb所示的恒流源电路在 A端施加了正向电压但 电压小于正向恒流起始电压 VK时，电压升高会使得 B端电流也增加而与所施加 的电压近似成线性关系。 当电压继续升高时， 流出 B端的电流保持不变。 当 A 当上施加的电压升高到 VB时， 电流突然陡增而出现类似于雪崩二极管的特性。 但是当电路处于反向偏压时， 图 la和图 lb所示的恒流源电路是不具有恒流源 特性的。 另外， 由于当今的半导体电路通常制成集成电路形式， 当图 la和图 lb所 示的恒流源电路做成集成电路时， 它通常具有 3个或以上的引脚端子。 因此， 三端子或三端子以上的恒流源电路装配相对比较复杂， 使用不太方便。 发明内容It can be seen from Fig. 2 that the constant current source circuit shown in Fig. 1a and Fig. 1b applies a forward voltage at the A terminal but the voltage is lower than the forward constant current starting voltage VK , and the voltage rise causes the B terminal current to also The increase is approximately linear with the applied voltage. When the voltage continues to rise, the current flowing out of the B terminal remains unchanged. When A applied voltage rises to VB , the current suddenly increases sharply and a characteristic similar to an avalanche diode occurs. However, when the circuit is in reverse bias, the constant current source circuit shown in Figures la and lb does not have constant current source characteristics. In addition, since today's semiconductor circuits are usually fabricated in the form of integrated circuits, when the constant current source circuits shown in Figs. 1a and 1b are formed as integrated circuits, they usually have three or more pin terminals. Therefore, the three-terminal or three-terminal constant current source circuit assembly is relatively complicated and inconvenient to use. Summary of the invention
本发明的目的是提供一种恒流源电路结构， 这种恒流源电路只具有两个 引脚端子。 SUMMARY OF THE INVENTION An object of the present invention is to provide a constant current source circuit structure having only two pin terminals.
本发明的恒流源电路包含： 第一晶体管； 以及第二晶体管， 其中， 第一 晶体管的源极和其栅极耦合， 而第二晶体管的源极和其栅极耦合， 其中， 第 一晶体管的漏极和第二晶体管的漏极互相耦合在一起， 从而， 所述第一晶体 管的源极和其柵极相耦合的端子以及所述第二晶体管的源极和其栅极相耦合 的端子构成由所述第一晶体管和所述第二晶体管形成的一个二端子元件的两 个端子。 The constant current source circuit of the present invention includes: a first transistor; and a second transistor, wherein a source of the first transistor is coupled to a gate thereof, and a source of the second transistor is coupled to a gate thereof, wherein the first transistor a drain and a drain of the second transistor are coupled to each other such that a terminal of the first transistor is coupled to a gate thereof and a terminal of the second transistor is coupled to a gate thereof Two terminals of a two-terminal element formed by the first transistor and the second transistor are formed.
本发明的恒流源电路结构中， 第一晶体管和第二晶体管是双扩散金属氧 化物半导体（DMOS ) 场效应晶体管。 In the constant current source circuit structure of the present invention, the first transistor and the second transistor are double diffused metal oxide semiconductor (DMOS) field effect transistors.
本发明的恒流源电路结构中， 第一晶体管和第二晶体管也可以是 PN结型 场效应晶体管 （JFET)。 In the constant current source circuit structure of the present invention, the first transistor and the second transistor may also be PN junction field effect transistors (JFETs).
本发明的恒流源电路结构中 , 两个双扩散金属氧化物半导体场效应晶体 管具有对称的正反向伏安特性。 In the constant current source circuit structure of the present invention, two double-diffused metal oxide semiconductor field effect transistors have symmetric forward and reverse volt-ampere characteristics.
本发明的恒流源电路结构中 , 两个 PN结型场效应晶体管具有对称的正反 向伏安特性。 In the constant current source circuit structure of the present invention, the two PN junction field effect transistors have symmetric forward and reverse volt-ampere characteristics.
采用本发明的恒流源电路结构， 装配简单， 使用方便。 附图说明 The constant current source circuit structure of the invention is simple in assembly and convenient to use. DRAWINGS
图 1 a是现有技术中采用沟道型金属氧化物场效应晶体管构成的恒流源电 路； 图 lb是现有技术中釆用双极结晶体管构成的恒流源电路； 其中， I参考是 A 端中的参考电流， ¾是 B端中的输出电流， Vcc是偏置电压， ΙΒΑ^极电流； 图 2示出的是图 la、 lb所示现有技术的恒流源电路的输入 /输出伏安特性； 图 3a是本发明一种实施例采用耗尽型 DMOS对称设计的双向恒流源电路 示意图；1 a is a constant current source circuit formed by using a channel type metal oxide field effect transistor in the prior art; FIG. 1b is a constant current source circuit formed by using a bipolar junction transistor in the prior art; wherein, the I reference is a terminal of the reference current, ¾ is the output current of terminal B, Vcc is the biasvoltage, Ι Β Α ^ current electrode; 2 is an input/output volt-ampere characteristic of the prior art constant current source circuit shown in FIGS. 1a and 1b; FIG. 3a is a bidirectional constant current source circuit using a depletion mode DMOS symmetric design according to an embodiment of the present invention; schematic diagram;
图 3b是本发明一种实施例采用结场效应晶体管对称设计的双向恒流源电 路； FIG. 3b is a bidirectional constant current source circuit symmetrically designed by using a junction field effect transistor according to an embodiment of the present invention; FIG.
图 4是图 3a和图 3b所示本发明双向恒流源电路的输入 /输出伏安特性； 图 5是本发明的双向恒流源集成电路外形示意图； 4 is an input/output volt-ampere characteristic of the bidirectional constant current source circuit of the present invention shown in FIGS. 3a and 3b; FIG. 5 is a schematic view showing the outline of the bidirectional constant current source integrated circuit of the present invention;
图 6是图 3a或图 3b所示两个耗尽型金属氧化物半导体（MOS )恒流源结构 或两个结场效应晶体管恒流源结构的平面结构示意图； 而 Figure 6 is a plan view showing the planar structure of two depletion-mode metal oxide semiconductor (MOS) constant current source structures or two junction field effect transistor constant current source structures shown in Figure 3a or Figure 3b;
图 7是两个耗尽型 MOS恒流源结构单元的元胞的纵向结构示意图。 具体实施方式 Fig. 7 is a schematic view showing the longitudinal structure of cells of two depletion type MOS constant current source structural units. detailed description
下面参照附图， 描述本发明的双向恒流源电路的结构。 The structure of the bidirectional constant current source circuit of the present invention will be described below with reference to the accompanying drawings.
DMOS是一种由源极、 漏极和栅极构成的双扩散金属氧化物半导体场效 应晶体管电路。 它有两种类型。 一种是垂直双扩散金属氧化物半导体场效应 晶体管电路 VDMOSFET ( vertical double-diffused MOSFET ); 另一种是横向双 扩散金属氧化物半导体场效应晶体管电路 LDMOSFET ( lateral double-diffused MOSFET )。 DMOS is a double-diffused metal oxide semiconductor field effect transistor circuit composed of a source, a drain and a gate. It comes in two types. One is a vertical double-diffused metal oxide semiconductor field effect transistor circuit VDMOSFET (vertical double-diffused MOSFET); the other is a lateral double-diffused metal-oxide-semiconductor field-effect transistor circuit LDMOSFET (axial double-diffused MOSFET).
DMOS的性能主要由它的导通电阻 Rds(on)决定。 导通电阻 Rds(on)指的是 DMOS工作时从漏极到源极的电阻。 当 Rds(on)很小时， 恒流源电路将具有很 优良的开关特性， 从而会有较大的输出电流， 使得电路具有较强的电流驱动 能力。The performance of DMOS is mainly determined by its on-resistance Rds (on). The on-resistance Rds (on) refers to the resistance from the drain to the source when the DMOS is operating. When Rds (on) is small, the constant current source circuit will have excellent switching characteristics, which will result in a large output current, making the circuit have a strong current driving capability.
利用 DMOS的这一特性， 就制成了如图 3a所示的耗尽型 DMOS的恒流 源电路。 Using this characteristic of DMOS, a constant current source circuit of a depletion type DMOS as shown in Fig. 3a is fabricated.
如图 3a所示， 将两个 DMOS的漏极鵜合起来。 由于两个 DMOS的漏极 是相耦合的， 所以如图 3a 所示的连接方法就构成了一种对称结构的 DMOS 恒流源电路。 最好选择两个伏安特性相同的 DMOS元件。 这样就可以使得对 称结构的 DMOS恒流源电路正反向的伏安特性具有完全的对称性。As shown in Figure 3a, the drains of the two DMOS are twisted together. Since the drains of the two DMOSs are coupled, the connection method shown in Figure 3a constitutes a symmetrical DMOS constant current source circuit. It is best to choose two DMOS components with the same volt-ampere characteristics. This will make it right The volt-ampere characteristics of the forward and reverse directions of the DMOS constant current source circuit of the structure are completely symmetrical.
由于 DMOS的漏 -源导通电阻 4艮小， 因此， 如图 3a这种结构的 DMOS 恒流源电路就可以在正向偏压和反向偏压的分别作用下， 都可以具有 4艮好的 开关特性， 从而在 A端和 B端都可以提供很好的恒流电流。 这是因为， 当在 A端上加上反向偏压时， 这相当于在 B端上加上了正向偏压； 而当在 A端上 加上正向偏压时， 就相当于在 B端上加上了反向偏压。 因此， 无论所加的偏 压对一个晶体管来说是正向的还是反向的， 都会改变两个晶体管中的其中一 个晶体管的沟道区的厚度， 从而使输出电流为恒定。 Since the drain-source on-resistance 4 of the DMOS is small, the DMOS constant current source circuit of the structure of Fig. 3a can have 4 turns under the action of forward bias and reverse bias respectively. The switching characteristics provide a good constant current at both the A and B terminals. This is because when a reverse bias is applied to the A terminal, this is equivalent to adding a forward bias to the B terminal; and when a forward bias is applied to the A terminal, it is equivalent to A reverse bias is applied to the B terminal. Therefore, regardless of whether the applied bias voltage is positive or negative for one transistor, the thickness of the channel region of one of the two transistors is changed, so that the output current is constant.
另一种电路结构是用 JFET (即 PN结型场效应晶体管）构成的恒流源电 路结构。 Another circuit structure is a constant current source circuit structure constructed using a JFET (i.e., a PN junction field effect transistor).
这种结构的场效应晶体管的原理是在 N型半导体基片上或者 P型半导体 基片上制作一对 PN结及相应的金属电极。在这两个 PN结之间形成导电沟道， 通过改变外加 PN结的反向偏压， 以改变 PN结耗尽层的厚度， 从而改变沟道 区载流子的密度并进而控制通过沟道输出的电流。 The principle of the field effect transistor of this structure is to fabricate a pair of PN junctions and corresponding metal electrodes on an N-type semiconductor substrate or a P-type semiconductor substrate. Forming a conductive channel between the two PN junctions, changing the thickness of the PN junction depletion layer by changing the reverse bias of the applied PN junction, thereby changing the density of the carrier in the channel region and thereby controlling the passage through the channel The current output.
图 3b示出了将两个 JFET晶体管的漏极 合起来后组成的一个恒流源电 路的情况。 与图 3a示出的情况类似， 图 3b示出了对称结构的 JFET恒流源电 路的结构。 最好选择两个伏安特性相同的 JFET元件。 这样就可以使得对称结 构的 JFET恒流源电路正反向的伏安特性具有完全的对称性。 Figure 3b shows the case of a constant current source circuit composed by combining the drains of two JFET transistors. Similar to the case shown in Fig. 3a, Fig. 3b shows the structure of a JFET constant current source circuit of a symmetrical structure. It is best to choose two JFET components with the same volt-ampere characteristics. This allows the symmetrical characteristics of the forward and reverse volt-ampere characteristics of the symmetric JFET constant current source circuit to be completely symmetrical.
由于图 3b示出的两个 JFET是对称耦合的， 所以， 当在 A端上加上反向 偏压时， 可以改变左边那一个 JFET的 PN结的耗尽层厚度， 从而改变左边那 一个 JFET的沟道区载流子的密度并进而控制通过其沟道输出的电流。 而当在 B端加上反向偏压时， 可以改变右边那一个 JFET的 PN结的耗尽层厚度， 从 而改变右边那一个 JFET 的沟道区栽流子的密度并进而控制通过其沟道输出 的电流。 因此，无论对哪一个晶体管来说所施加的偏压是正向的还是反向的， 由于电路的对称结构， 都将在所施加的电压足够大时， 使正向和反向有恒定 电 输出。 Since the two JFETs shown in Figure 3b are symmetrically coupled, when a reverse bias is applied to terminal A, the depletion layer thickness of the PN junction of the left JFET can be changed, thereby changing the JFET on the left. The density of the carrier in the channel region and thus the current output through its channel. When a reverse bias is applied to the B terminal, the thickness of the depletion layer of the PN junction of the JFET on the right side can be changed, thereby changing the density of the channel region of the JFET on the right side and controlling the channel through it. The current output. Therefore, no matter which transistor the applied bias voltage is positive or negative, due to the symmetrical structure of the circuit, there will be a constant electrical output in the forward and reverse directions when the applied voltage is sufficiently large.
图 4示出的是图 3a或图 3b所示恒流源电路结构的输出伏安特性的示意 图。 图 4中可以看出， 无论在 A端施加的是正向偏压还是反向偏压， 电路输 出的都是饱和电流。Figure 4 is a schematic illustration of the output volt-ampere characteristics of the constant current source circuit structure shown in Figure 3a or Figure 3b. Figure. As can be seen in Figure 4, the circuit outputs a saturation current regardless of whether forward bias or reverse bias is applied at terminal A.
图 4中， VK是正向恒流起始电压； Ip是正向恒定电流； VB是正向恒流结 束电压； VKR是反向恒流起始电压； VBR 反向恒流结束电压； IPR是反向恒定 电流； 而 VR是恒二极管反向电压。In Figure 4, VK is the forward constant current starting voltage; Ip is the forward constant current; VB is the positive constant current ending voltage; VKR is the reverse constant current starting voltage; VBR is the reverse constant current ending voltage; IPR Is the reverse constant current; and VR is the constant diode reverse voltage.
如图 4所示， 当图 3a或图 3b所示的两个元件（1, 2) 的漏极輛合在一 起时， 如杲施加在 A端上的电压小于 Vk， 相当于在元件（ 1 )上施加了一个 正向电压， 因而从 B端输出的电流 I与 A上施加的电压近似成线性关系。 当 施加在 A端上的正向电压继续升高时， 元件（ 1 )就进入饱和区， 从而 B端输 出的电流维持使得元件（ 1 )的饱和电流 Ip不变。 当施加在 A端的电压升高到 元件（1 ) 的击穿电压时， B 端的电流呈现出元件 （1 ) 出现雪崩电流， 而使 得电流突然陡增。As shown in FIG. 4, when the drains of the two elements (1, 2) shown in Fig. 3a or Fig. 3b are brought together, if the voltage applied to the terminal A is less thanVk , it corresponds to the component ( 1) A forward voltage is applied, so that the current I output from the B terminal is approximately linear with the voltage applied to A. When the forward voltage applied to the A terminal continues to rise, the component (1) enters the saturation region, so that the current outputted at the terminal B is maintained such that the saturation current Ip of the component (1) does not change. When the voltage applied to terminal A rises to the breakdown voltage of element (1), the current at terminal B exhibits avalanche current in element (1), causing the current to suddenly increase sharply.
由于本发明中元件（ 1 )和（ 2 )是对称设计的 , 因而当 B端施加了电压 时， 在 A端上出现的电流变化情况与上面是相同的。 Since the elements (1) and (2) of the present invention are symmetrically designed, when a voltage is applied to the terminal B, the current change occurring at the terminal A is the same as above.
图 6示出了图 3a或图 3b所示两个耗尽型金属氧化物半导体（MOS)恒 流源结构或两个结场效应晶体管恒流源结构的平面结构示意图。 图 6 中， 区 域（ 3 )是金属铝层 , 区域（ 4 )是介质层（如二氧化硅等）， 中间的环形区域 ( A )、 (B)是栅极和源极区域。 Fig. 6 is a plan view showing the planar structure of two depletion metal oxide semiconductor (MOS) constant current source structures or two junction field effect transistor constant current source structures shown in Fig. 3a or Fig. 3b. In Fig. 6, the region (3) is a metal aluminum layer, the region (4) is a dielectric layer (such as silicon dioxide, etc.), and the intermediate annular regions (A) and (B) are gate and source regions.
图 7是两个耗尽型 MOS恒流源结构单元的元胞的纵向剖面结构示意图。 从图 7可以进一步了解本发明的耗尽型 DMOS恒流源结构单元的元胞内部结 构， 其中， （5)是金属铝， （6)是介质层（如 SiO2), (7)是多晶层， （8)是 栅氧化层， （9)是 N+掺杂区， （10)是 P-掺杂区， （11 )是 N-材料， （12) 是装片底座。 由于^ ^型 DMOS为本领域技术人员公知的一种半导体器件， 这里就不再赘述。Fig. 7 is a schematic longitudinal sectional view showing the cells of two depletion type MOS constant current source structural units. The internal structure of the cell of the depletion type DMOS constant current source structural unit of the present invention can be further understood from FIG. 7, wherein (5) is a metal aluminum, (6) is a dielectric layer (such as SiO2 ), and (7) is more The crystal layer, (8) is a gate oxide layer, (9) is an N+ doped region, (10) is a P-doped region, (11) is an N-material, and (12) is a mounted substrate. Since the ^^ type DMOS is a semiconductor device known to those skilled in the art, it will not be described here.
采用本发明所得到的恒流源电路具有如图 5 所示的二端外形结构， 从而 使得电路变得简单， 使用方便。 The constant current source circuit obtained by the invention has a two-terminal outline structure as shown in Fig. 5, thereby making the circuit simple and convenient to use.
上文中， 参照附图描述了本发明的具体实施例。 但是， 本领域中的普通 技术人员能够理解， 在不偏离本发明的原理和精神的情况下， 还可以对本发 明的上述实施例作某些修改和变更。 实施例的描述仅仅是为了使本领域中的 普通技术人员能够理解、 实施本发明， 不应当将本发明理解为仅仅限于所描 述的实施例。 本发明的保护范围由权利要求书所限定。Hereinabove, specific embodiments of the present invention have been described with reference to the drawings. However, ordinary in the field A person skilled in the art can understand that certain modifications and changes can be made to the above-described embodiments of the present invention without departing from the spirit and scope of the invention. The description of the embodiments is merely intended to enable a person skilled in the art to understand and practice the invention, and the invention should not be construed as being limited to the described embodiments. The scope of the invention is defined by the claims.