Help with Constant Current Source

[rajesheee_244]

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]

**broken link removed**

 

[colin55]

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**

 

[rajesheee_244]

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

 

[Gayan Soyza]

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

 

[edeca]

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