DigiTan
New Member
I'm having trouble getting a very simple circuit to work. It's my understanding that the circuit shown below is supposed to saturate and drive the collector voltage down to almost zero so that the LED will illuminate. When I try it on my breadboards and PCBs with 2N2222A transistors, the collector voltage stays close to 5V and the collector current is miniscule (less than 1mA). What the heck is going on here? Are the transistors fried or is it the circuit? (I've had these transistors for almost 12 years, so damage may be a factor. They all tested fine, though.)
**broken link removed**
Also, I want to replace the LED with an LCD display backlight. Can this system be used to switch this kind of load as well?
**broken link removed**
Also, I want to replace the LED with an LCD display backlight. Can this system be used to switch this kind of load as well?