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.

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.

$I_{R 2} (= I_{E}) = \frac{V_{R 2}}{R 2} = \frac{V_{Z} - V_{B E}}{R 2}$

$R 2 = \frac{V_{Z} - V_{B E}}{I_{R 2}}$ or $R 2 = \frac{V_{Z} - 0.65}{I_{R 2}}$ , 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

$R_{2} = \frac{V_{Z} + V_{D} - V_{B E}}{I_{R 2}}$

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

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

(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

$R_{2} = \frac{V_{D} - V_{B E}}{I_{R 2}}$

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

مصادر التيار عالي الجهد

مقارنة مصادر الجهد والتيار

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.

[1]

[2]

[3]