Booster hFE

[vendettav]

hey guys
i tried out a sekova booster http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album14/album143/SEKOVA_POWER_BOOSTER_VERO_001.gif.html

the thing is i tried a few transistors and narrowed it down to 2n3904 (hFE 140~), a BC18AC (460~) and an unknown NPN witha blue dot on top. i'll call it a Blue NPN (650~)

kinda sounds like the same tho there's a bit of difference. now the question is what hFE do you need for clean boost?

PS. you think sekova is a nice pick for a simple booster?

cheers V

[Gus]

That is a simple textbook transistor circuit.  Google Bing look in books for how it works.
The biasing used is a predictable type.  Most small signal transistors will bias.  The Hfe will change the input resistance.  Most of the input resistance is due to the 43K resistor in the bias string.

Look for the LPB

You should know just by looking at the schematic the input resistance is less than 43K.  Fast calculation 1/ (Hfe X 390) + 1/43K +1/430K = 1/input resistance

You should also know the gain will be less the 10000/390 just by looking at the circuit

Have you looked at the beginner boost.  IMO not a good name for it.

[vendettav]

thanx gus, I totally forgot about the beginner boost. that thing isn't that far from the one i got up there. hope i'll breadboard it tmaro

and about the formulas. ahh we'll i've skipped the lessons on theory in my school haha. mind giving me some nice links to some reads?