PUMH13 - NPN-NPN

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Hi !

 

I'm using PUMH13 to drive LEDs.

 

 

 

My question is, is there similar chip with but with extra resistor in collector pin (form pin 3 and 6 to collector of TR1 and TR2) so external resistor is series with LED is not needed.

 

You know what I mean..

 

 

Thank you !

 

 

 

 

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mesko wrote:
You know what I mean

I think I do - but, to avoid any doubt, why don't you just draw it?!

 

The whole reason we have circuit diagrams - aka schematic diagrams - is that this stuff is so much easier to convey in the form of a diagram!!

 

mesko wrote:
to drive LEDs
 

If you're looking for a chip to drive LEDs (of which plenty are available), they would normally use a current source ...

 

 

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Hi !

 

here is schematics.

 

In rectangle is PUMH13 TR1 , I would like to have a chip that has R3 also inside. That's all.

 

 

 

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like I said, this is normally achieved in LED driver chips as a current source - not a series resistor.

 

Not sure that this type of resistor is kind of thing that goes well with silicon integration ... ?

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mesko wrote:
You know what I mean..
Yea ... still need to limit the current somehow.

Following is similar to PUMH13 :

Diodes

Diodes

Back to Discrete - LED Driver Solutions

AL5802

30V Adjustable Current Sink Linear LED Driver

https://www.diodes.com/products/discrete/functional-arrays/discrete-led-driver-solutions/part/AL5802

...

The AL5802 combines a high gain NPN transistor with a prebiased NPN transistor to make a simple small footprint LED driver. The LED current is set by an external resistor connected to from REXT pin (6) to GND pin (4), the internal high gain transistor develops approximately 0.6V across the external resistor.

...

The AL5802 is available in a SOT26 package and is ideal for driving 20mA to 120mA LED currents.

...

 


https://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyPUMH13115

https://www.mouser.com/new/diodes-inc/diodesAL5802/

 

"Dare to be naïve." - Buckminster Fuller

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While convenient having the resistor inside the chip is not practical for two reasons.  One you would not be able to tailor the resistor to the LED'a current requirements unless you change it's drive voltage, which may not be possible.  Two, this would be a manufacturing headache as the vendor would need to have several assembly lines to produce the many variants.  This is not economical to the vendors bottom line.

 

Besides, it would end up costing you more to buy a part with the resistor integrated as opposed to a $0.05 chip resistor.

 

JIm
 

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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If I go to Digikey and search "LED driver", it comes up with hundreds of hits including this: https://www.diodes.com/assets/Da...

That has a 10mA preset current, but may be overridden with an optional external resistor.  

 

Jim

 

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There is a very wide range of LEDs in terms of their forward voltage, and their drive current.

 

There is a wide range of possible drive voltages the transistor can handle.

 

Hence, almost an infinite combination of possibilities, as Jim mentioned above.

 

Hence, use the external resistor to set the current level!

 

JC

 

 

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DocJC wrote:
 use the external resistor to set the current level!

or, as I think someone might have mentioned, use an LED driver ...

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Agreed,

 

But the OP started down the path of using a simple resistor current limiter approach, which is cheap and easy.

 

Clearly if the OP was driving the LED from an AVR they likely would not even need the transistor!

 

When driving a string of LEDs, or using high current LEDs, the smart LED driver chips make it easy.

 

For a simple project with a generic LED, a resistor is cheap and works.

 

Lots of options!

 

JC