Help with Constant Current Source

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rajesheee_244

New Member

• Apr 11, 2012

• #1

Hi...can anyone please help me out? I need to design a current source with current ratings range 1mA - 50mA and with a compliance voltage of 50v. Can anyone help me in designing the circuit? Thank you in advance.

 

ronsimpson

Well-Known Member

Most Helpful Member

• Apr 12, 2012

• #2

**broken link removed**

 

C

colin55

Well-Known Member

• Apr 12, 2012

• #3

CONSTANT CURRENT SOURCE
The output will be limited to 1mA by using a red LED and 1k for Re.
The output will be limited to 100mA by using a red LED and 10R for Re.
Use a pot to vary the output.

**broken link removed**

 

Last edited: Apr 12, 2012

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rajesheee_244

New Member

• Apr 16, 2012

• #4

@colin55 : can you please explain the operation of the circuit which you have shown in your post...thank

 

Gayan Soyza

Active Member

• Apr 16, 2012

• #5

Since 330R is ground the transistor is switched ON.

LED voltage is equivalent to V(BE) + V(Re)

Assume an Red LED needs 2V.

2V = 0.7V + VRe
VRe = 1.3V ---- voltage across (Re)

Using ohms law to (Re)
1.3 = I X 1000R
I = 1.3mA

 

Last edited: Apr 16, 2012

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edeca

Active Member

• Apr 16, 2012

• #6

Depending on your actual requirements you might find that an LED driver IC does what you need. They are designed to operate with high voltages and can have the current set by an external resistor.

These two look like nice drivers:

https://www.electro-tech-online.com/custompdfs/2012/04/NUD4011-DPDF.pdf
https://www.electro-tech-online.com/custompdfs/2012/04/CAT4002A-DPDF.pdf