مصدر تيار

تحليل خطي للشبكات
العناصر

المكونات

دوائر التوالي والتوازي

تحويلات المعاوقة

مبرهنات المولد	مبرهنات الشبكة

أساليب تحليل الشبكات

Two-port parameters

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مصدر التيار، هو جهاز إلكتروني أو كهربائي يقوم بتوصل التيار الكهربائي.

Figure 1: An ideal current source, I, driving a resistor, R, and creating a voltage V

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مصادر الكهرباء القياسية


Voltage source	Current Source

Controlled Voltage Source	Controlled Current Source

Battery of cells	Single cell

Figure 2: Source symbols

مصادر التيار الفيزيائية

Resistor current source

Active current sources

JFET and N-FET current source

Simple transistor current source

Figure 3: Typical constant current source (CCS)

Voltage across R2 (V_R2) is given by V_Z - V_BE, where V_BE is the base-emitter drop of Q1.

$I_{R2}(=I_{E})={\frac {V_{R2}}{R2}}={\frac {V_{Z}-V_{BE}}{R2}}$

$R2={\frac {V_{Z}-V_{BE}}{I_{R2}}}$ or $R2={\frac {V_{Z}-0.65}{I_{R2}}}$ , since V_BE is typically 0.65 V for a silicon device.^[1]

Simple transistor current source with diode compensation

Figure 4: Typical constant current source (CCS) with diode compensation

Resistance R₂ is now calculated as

$R_{2}={\frac {V_{Z}+V_{D}-V_{BE}}{I_{R2}}}$

Since V_D = V_BE = 0.65 V,^[2]

Therefore, $R_{2}={\frac {V_{Z}}{I_{R2}}}$

(In practice V_D is never exactly equal to V_BE and hence it only suppresses the change in V_BE rather than nulling it out.)

and R₁ is calculated as

$R_{1}={\frac {V_{S}-V_{Z}-V_{D}}{I_{Z}+K\cdot I_{B}}}$ (the compensating diode's forward voltage drop V_D appears in the equation and is typically 0.65 V for silicon devices.^[3])

Simple transistor current source with LED

Figure 5: Typical constant current source (CCS) using LED instead of zener

$R_{2}={\frac {V_{D}-V_{BE}}{I_{R2}}}$

and R₁ as

$R_{1}={\frac {V_{S}-V_{D}}{I_{D}+K\cdot I_{B}}}$ , where I_D is the LED current.

التغذية

Figure 6: Typical op-amp current source. The transistor is not needed if the required current doesn't exceed the sourcing ability of the op-amp. The current will be the zener voltage divided by the sense resistor.

تيار منعكس

مصادر عملي أخرى

Inductor type current source

Figure 7: Constant current source using the LM317 voltage regulator

مصادر التيار عالي الجهد

مقارنة مصادر الجهد والتيار

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انظر أيضا

Voltage-to-current converter
تيار منعكس
Iron-hydrogen resistor
Widlar current source
Wilson current source
Current loop
Welding power supply, a device used for arc welding, many of which are designed as constant current devices.
Current sources and sinks

المصادر والهوامش

^ The value for V_BE varies logarithmically with current level: for more detail see diode modelling.
^ See above note on logarithmic current dependence.
^ See above note on logarithmic current dependence.

قراءات اضافية

"Current Sources & Voltage References" Linden T. Harrison; Publ. Elsevier-Newnes 2005; 608-pages; ISBN 0-7506-7752-X

وصلات خارجية

[1] The value for V_BE varies logarithmically with current level: for more detail see diode modelling.

[2] See above note on logarithmic current dependence.

[3] See above note on logarithmic current dependence.

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[2]

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