Thank you idy and Eb7/9+ I have two more questions about transistors:

1) Having a lot of 2N3904 with hfe between 120-150 (*) and others with hfe between 248-260 (*), which set should I prefer for the unit? 
(*)=measured on the socket of my digital multimeter

2) I would like to use a TO-220 for the Q13 transistor instead of a TO-92 (the pcb I bought has both choices implemented). Is there a TO-220 case for the 2N3904? If not, which TO-220 NPN could I use?


Thankyou again

TO-220 is a package for medium power transistors..
(safely dissipating more than 1W without heat-sinking..)

Those transistors have low h_fe (less than 20, minimum..)

You can use TO-220 Darlingtons (like BD645/647/649/651) or less powerful TO-126 (like BD675/677/679/681)..

Of course, any discrete Darligton configuration (e.g. 2N3904 + TIP31) should be fine..

P.S.
IMHO, any general purpose TO-92 BJT should manage to drive  the lamp without heating issues..
(take into account that its power dissipation isn't constant but is strongly related to LFO's duty cycle..)

Quote from: antonis on February 07, 2024, 06:50:18 AMTO-220 is a package for medium power transistors.. (safely dissipating more than 1W without heat-sinking..)Those transistors have low h_fe (less than 20, minimum..)
......
P.S.
IMHO, any general purpose TO-92 BJT should manage to drive  the lamp without heating issues..
(take into account that its power dissipation isn't constant but is strongly related to LFO's duty cycle..)

Thankyou, I think I will use TO-92 because TO-220 are too low in h_fe.
The duty cycle should be independent of the LFO frequency, right? Or in the case of Neovibe does it depend on the frequency of the LFO?

Quote from: parser on February 07, 2024, 10:21:16 AMThe duty cycle should be independent of the LFO frequency, right? Or in the case of Neovibe does it depend on the frequency of the LFO?

R.G.'s analysis