# tri state diode

Discussion in 'Electronic Design' started by Tuurbo46, Sep 23, 2004.

1. ### Tuurbo46Guest

Hi

Whats the foward voltage drop across a tri state LED diode. I know a
coventional LED is 1.2v. Also im currently working in Proteus ISIS
schematic program and i cant find the part in the libary. Is it best
represented by 3 LED's in series.

Cheers Turbo

2. ### Spehro PefhanyGuest

What exactly is a "tri-state diode"? Do you mean a bipolar dual-color
LED?

AFAIK, no (visible) LEDs have typical voltage drop as low as 1.2V at
reasonable operating currents. More like 1.6 to 3.2V, depending on LED
color, LED type, and operating current.

Best regards,
Spehro Pefhany

3. ### John FieldsGuest

---
Is that a question.

A tri-state LED is two LEDs in the same lamp connected in either
series aiding or series opposition or in parallel opposition:

Series aiding:

+>--[LED>]--+
|
COM>--------+
|
->--[<LED]--+

Series opposed:

+>--[LED>]--+
|
COM>--------+
|
+>--[LED>]--+

Parallel opposed:

+--[LED>]--+
| |
+/->---+--[<LED]--+
|
-/+>--------------+

The voltage drop across each LED will vary, basically, depending on
the color of the light it emits.

4. ### Spehro PefhanyGuest

Your first two have 4 possible 'states', if you count 'off'.

Best regards,
Spehro Pefhany

5. ### John FieldsGuest

---
State 1 = color 1

State 2 = color 2

State 3 = color 1 and color 2. For the series cases, DC will do it.
For the parallel case, polarity reversals faster than the persistence
of vision will.

6. ### Spehro PefhanyGuest

How fast does your persistence reverse?

Best regards,
Spehro Pefhany

7. ### John WoodgateGuest

I read in sci.electronics.design that Spehro Pefhany <[email protected]
It depends on how loudly she screams. (;-)

8. ### John FieldsGuest

.... polarity reversals faster than vision will be able to follow.

Better?

10. ### Spehro PefhanyGuest

<LOL>

Best regards,
Spehro Pefhany