什么是当前镜子:电路及其工作

用于设计整体型integrated circuit, the most popular technique is used namely the current mirror. So in this method, the designing of the circuit can be done to copy the flow of current throughout one energetic device to another including the feature of current control. Here, the flow of current can be copied in the form of inverting from device to device. Once the flow of current within the first active device is altered then the reflected output current from the other active device will also be changed. Therefore, the current mirror circuit is frequently referred to as a CCCS (Current Controlled Current Source). This article discusses an overview of the current mirror circuit and its working.

什么是当前镜子?

T.He circuit is used to copy the flow of current in one active device and controlling the flow of current in another device by maintaining the output current stable instead of loading is known as a current mirror. Theoretically, a perfect current mirror is an inverting currentamplifier. The main function of this amplifier is to reverse the direction of the flow of current. The main function of the current mirror is to provide active loads as well as bias currents to circuits and also used to form a more practical current source.


Current Mirror Circuit

一般的ly, the designing of current mirror circuits can be done with two maintransistorsand even though other devices like FETs also used. Some of these circuits may utilize the above two transistors for allowing the performance level to be enhanced. As the name suggests, it copies the flow of current in one active device whereas, in another active device, it maintains the output current stable instead of loading. The copied current is a constant current.

Current Mirror Circuit
Current Mirror Circuit

电流镜电路图如下所示。该电路可以用两个晶体管构建,其中一个晶体管基座和收集器端子连接,而其他一个晶体管基座和收集器端子在其他情况下也没有。在电路中,两个晶体管的基端子都连接,而发射器端子被提供给GND。在该电路中,两个晶体管都类似地工作。

在circuit operation, the base-emitter terminals of the first transistor (TR1) work as a diode because the collector and base terminals are connected together.

朝向TRI晶体管的电流流动通过其他方式进行外部设置组件, and consequently, there is a specified voltage developed across the BE junction of the first transistor. When the BE voltage on these two transistors is the same, then the flow of current within one transistor will accurately mirror the second transistor. So, the flow of current into the first transistor will be reflected into the second transistor & therefore into the R1 load.


Wilson Current Mirror

电流镜电路的变化称为Wilson电流镜电路,因为该晶体管包括另一个晶体管状TR3。威尔逊电流镜的电路图如下所示。在电路中,TR3晶体管将第一晶体管(TR1)的集电极端子保持在等于VCC下方的两个二极管的电压。

威尔逊电路
威尔逊电路

T.His circuit overcomes the earlier effect and it is extremely useful, particularly in ICs or集成电路. The different components can be used simply in the circuit design. They allow unbiased currents to flow into the circuits such as differential pairs & this makes sure that their function is enhanced further. These mirrors are not extensively used external IC technology in view of the extra number of components necessary, however, the principles are similar in both discrete form & once used in ICs.

Limitations of Current Mirror

使用上面讨论的两个晶体管的电流镜电路可能频繁地足以用于大多数应用程序。但它包括以下几种情况下的一些限制。

Current Changes with Change within Output Voltage

当由于O / P输出阻抗引起的输出电压变化而不是无限制时,电流的流量将改变,因为;通过在TR2晶体管内的指定电流下的集电极电压有一个小的“VBE”。通常,电流的流程可能会随输出符合范围的25%而变化。

Current Matching Lies on Transistor Matching

T.He matching of current mainly depends on the transistor matching. Frequently the transistors require to be on a similar substrate if they are to precisely reflect the current. These issues can be solved by using advanced current mirror circuits.

Current Mirror Circuit using MOSFET

T.His current mirror circuit can be implemented with twoMOSFETtransistors. This circuit working is similar to the previously discussed mirror circuit. The current mirror circuit using MOSFETs is shown below. In the following circuit, the two MOSFETs are considered as M1 and M2.

Current Mirror Circuit using MOSFET
Current Mirror Circuit using MOSFET

如Vds≤vgs,第一MOSFET,如M1,而M1的第二MOSFET,如果输出电压与饱和电压相比,输出电压较高,则第二MOSFET在饱和区域中。因此,第一MOSFET的输入电流可以控制第二MOSFET的O / P电流。
T.He function of MOSFET is, the drain current of this transistor replicates the function of the G to S and D to G voltage. So, by using the following function, the formula can be written.

一世D.=f (VGS, VDG.

Because of this, the M1 input current can be mirrored toward the drain current. The input current can be provided through the bias resistor. If the VDG is 0 for the M1, then the drain current of M1 will be

一世D.=f (VGS, VDG.=0.)

T.Hus, f (VGS, 0) = I一世Nso, I一世Nwill fix the VGS value. The same VGS can be reflected across the second MOSFET.

一世OUT=f (VGS, VDG.=0.)是真的。

因此,可以将O / P电流镜像,如I / P电流,一世OUT=一世一世N

Further, the VDS can be introduced like VDS.=V.DG.+ VGS. By changing this, the Shichman-Hodges model gives the estimated answer for theF(V.GS, VDG.. So this function can be expressed like the following.

一世D.=f (VGS, VDG.

一世D.=½ Kp (W/L) (VGS-VtH2(1+λVDS.

一世D.=½ Kp (W/L) (VGS-VtH2(1+λ(VDG.+ VGS))

T.He o/p resistance is calculated when the output resistance is limited

R.OUT=((1/ λ) +VDS.)/ID.as R = V/I

From the above equation,

Where ‘KP.'是晶体管技术相关的常数

‘W/L’ is the ratio of Width & Length

‘λ’ is mainly used for the channel length’s modulation constant.

‘VGS’ is the gate to source voltage

'Vth'是阈值电压

‘VDS.’ is a drain to source voltage

符合性电压,其中VDG = 0和MOSFET的电阻高,电流镜在较少的O / P电压范围内。可以通过导出这种情况来测量该电压。

V.简历=V.GS(ID.at VDG.= 0)

否则,F.-1(ID.)once the VDG.=0.

规格

T.He characterization of a current mirror circuit can be done by the following specifications.

Current Transfer Ratio

电流镜电路用于将一个有源设备的输入电流复制到其他有源器件的输出。这种电路也称为理想的电流放大器,包括替换设计,可以倾覆电流的方向。因此,电流传输比是电流放大器的重要因素。

一种C Output Resistance

R.esistance includes a VI relationship according to the ohms law. So, the resistance of AC o/p plays a key role within the output current’s stability with respect to changes in voltage.

电压下降

跨输出的工作镜电路的电压降较少。该电路可以工作的电压范围称为合规范围和该合规范围内的最低电压的最低电压被称为合规电压。保持晶体管主动的最小电压是必要的,因此最少的电压主要取决于晶体管的规格。

T.Hus, this is all about an overview of current mirror circuits like working and application of current mirror circuits.

使用BJT的电流镜电路

T.He current mirror circuit usingBJTs如下所示。假设这些晶体管equal so both the transistors operating temperatures as well as device parameters are similar. Since the VBE( base-emitter voltage) is the same for these transistors, then the IC1(reference current) for the Q1 transistor can be mirrored over the Q2 transistor that is IC2 = IC1 once the base currents are ignored. This permits us to modify IC2 irrespectively of the VC2 voltage through simply modifying the R1, as

使用BJT的电流镜电路
使用BJT的电流镜电路

一世C1.=V.CC.-0.7V / R1

一世f both the base currents like IB1.& IB2are used, then

一世C2.=一世C1./(1+(2 /β))

实际上,由于由于早期效果,“Q2”晶体管包括有限的输出电阻,IC2不与VC2相当独立。因此,可以发现IC2通过VC2略微扩增。
与VC2相比的IC2性能可以根据早期电压解释

一世C2.=一世s eV.BE2/V.T.(1 + vCE2/ V.一种

从上面的等式,'VA'是早期电压。因此,目前的镜子的O / P电阻可以写为

R.o = V一种/IC2.

Lastly, the BJTs should be in active mode to work the current mirror accordingly.

T.Hus, this is all about当前镜子的概述circuit and its working using BJTs, MOSFETs, Specifications, etc. Here is a question for you, what are the applications of the current mirror circuit?

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