مصدر تيار

تحليل خطي للشبكات
العناصر

المكونات

دوائر التوالي والتوازي

تحويلات المعاوقة

مبرهنات المولد	مبرهنات الشبكة

أساليب تحليل الشبكات

Two-port parameters

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

مصدر التيار، هوجهاز إلكتروني أوكهربائي 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.

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

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

Simple transistor current source with diode compensation

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

Resistance R₂ is now calculated as

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

Since V_D = V_BE = 0.65 V,

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

(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

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

Simple transistor current source with LED

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

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

and R₁ as

${\displaystyle R_{1 ={\frac {V_{S -V_{D {I_{D +K\cdot I_{B$ , 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

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.