350ma RED LED circuit design with resistors for voltage drop, current control

Hi,

I have a circuit made in PSpice, student version (pictured below). The circuit uses PSpice's D1N4148 diodes to represent ONE high power RED led which is rated at approximately 2.2 volts drop. I did this by adding three D1N4148 Diodes in series, which should be yielding 3 x 0.7v = 2.1v drop across the lines. But in this circuit, the model is showing that when I put the equivalency of 6 RED LEDS in parallel, the voltage drop is 3.4v which does not equal the projected 2.1v. Using a power source of 12vDC, you can see down below in _green_ the voltage drop across these diodes leaving 8.6v from the 12vDC power source, which means that the Vdrop across these diodes is 3.4v which does not equal 2.1v. Why is this the case?

What am I missing? Why would these models show that the diodes are dropping 1.13333 volts across each diode instead of 0.7volts?

* I NEED to use these resistors for the circuit - I realize that there are other ways of doing this. Can someone take a look at what I am working with here and give me any help?

SpecialtyLEDS said:

. . . . Why would these models show that the diodes are dropping 1.13333 volts across each diode instead of 0.7volts?
. . .

Click to expand...

Because if you read the datasheet for the 1N4148 you will see that at 330mA the voltage drop WILL be 1.1 volts.

SPICE doesn't do everything for you.

This diode is only rated for a continuous current of 200mA - use a diode within its ratings, like the 1N4001

MikeAusC

Thank you for taking the time to point me in the right direction. I will try the 1N4001.

May I ask you if there are indeed models available for download/import that represent the 350ma (red, green, blue) high power LEDs for PSPice student version? I will try to make sure where to find the datasheets for the parts listed in the most current PSpice Student Version Release 9.1.