what is the most efficient joule thief I can build with one transistor?

 

As a jewel thief, I use the three legged variety, as they run faster.

 

i mean the joule thief voltage elevator

 

The most efficient would used ideal components, but in reality you would probably choose a transistor with very high current gain and very low saturation voltage, a transformer with minimal wire resistance, a capacitor with minimal ESR.

 

thanks.and what can be the transistor you said?

 

thanks.and what can be the transistor you said?

It's all in the datsheets, you just have to look.

 

ok.but is there a way to make a joule thief more efficient by adding capacitor or other resistor?? or making the circuit LC resonant?

 

More efficient than what? You haven't posted a schematic of the circuit you have in mind.

 

the classical one transistor tapped coil circuit

 

the classical one transistor tapped coil circuit

Your words fail to communicate what you are talking about. A picture is worth several thousand words. Also how do you define and measure efficiency?

 

ok.but is there a way to make a joule thief more efficient by adding capacitor or other resistor?? or making the circuit LC resonant?

2 transistors. But...
http://www.electro-tech-online.com/...r-a-joule-thief-inspired-boost-regulator.594/

 

thank you

 

this is the basic version of the circuit I meant.

 

it is this

 

Hello,

The circuit you give is correct.
There are many ways to make the transformer.
On these pages there are some examples:
http://bigclive.com/joule.htm
http://www.evilmadscientist.com/2007/weekend-projects-with-bre-pettis-make-a-joule-thief/

Bertus

 

ok.thank you