LM334: Achieving higher currents than the LM334 supports

Luke Galea

Part Number: LM334
Other Parts Discussed in Thread: LM4041-N, TL431, LM317

Could someone recommend a good component that achieves a constant current of 50mA (so ideally a higher maximum output current not to run it at maximum load).

The LM334 has a limit of around 10mA, and I couldn't find more components on Texas Instruments that support higher currents...

over 4 years ago

0 Marcoo Z over 4 years ago

TI__Mastermind 19400 points

Hi Luke,

Are you looking for a current source or current sink?

IF you are looking for a current source, our best way is to use a LM4041-N ADJ and a FET to make a current source.

I would use a TL431 and a FET to make a current sink.

Both of these solutions are a bit bigger but they can provide you with a high current alternative to the precision LM334.

-Marcoo

0 Luke Galea over 4 years ago in reply to Marcoo Z

Intellectual 340 points

I need a current source, so I will check out the LM4041! ONLINE i have also found an LM317 being used as a current source, would you suggest that? It seems to be a similar concept to what you suggested.

0 Marcoo Z over 4 years ago in reply to Luke Galea

TI__Mastermind 19400 points

Hi Luke,

The LM317 does work as a current source. Nice find, we have such a large portfolio it can be difficult to find devices.

Both solutions work. The LM4041-N adj will provide a more accurate current over temperature but if you don't need the high precision then the LM317 will work.

-Marcoo

0 Luke Galea over 4 years ago in reply to Marcoo Z

Intellectual 340 points

Cheers! That's why I use these forums since people having experience can guide me better :) I'll have a look at the accuracy of the LM314 and see if it's enough.

0 Luke Galea over 4 years ago in reply to Luke Galea

Intellectual 340 points

Could somebody kindly explain the purpose of the 2N2905 and 2N3964 please? And whether a 12V supply can be used instead of 15V?

Thanks!

0 Luke Galea over 4 years ago in reply to Luke Galea

Intellectual 340 points

Could somebody kindly explain the purpose of the 2N2905 and 2N3964 please? And whether a 12V supply can be used instead of 15V?

Thanks!

0 Marcoo Z over 4 years ago in reply to Luke Galea

TI__Mastermind 19400 points

Hi Luke,

These PNP are in a darling ton configuration for higher current gain. The LM4041-N can only source up to 12mA and thus this limits the maximum current through the 2N2905. With the 2N3964, the 12mA is current boosted with this additional stage which allows a higher maximum current source.

-Marcoo

0 Luke Galea over 4 years ago in reply to Marcoo Z

Intellectual 340 points

Hi Marcoo,

Thank you for your reply. That sounds great :)

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LM334: Achieving higher currents than the LM334 supports