[sdiy] Driving LEDs from CMOS

[>>>marjan<<<]

> My problem comes from trying to drive an LED from this Q output.  I went from
> the Q output through a 47 ohm resistor to the base of a 2N3904.  Emitter to
> ground and collector through a 680 ohm current limiting resistor, then to the
>  LED.  The other LED leg goes to V+

47ohm is too low (too much current from logic) try better somethink in
1K-10K
range, also use two npns in darlington (both C to Vcc, B1 input, E1 to
B2,
E2 to serial 680ohm (or something) and LED to gnd), it's better to drive
it that way...


Cheers,


marjan