[sdiy] CMOS clock inputs.

[Dave Kendall]

Hi All.

Thanks everyone for the replies.

Rene, a couple of questions if you have the time...

> I would add a transistor with its emitter to GND, and a collector
> resistor in the neighbourhood of 4.7k to 15V. Then also a resistor at
> the base of 4.7k, and a diode from base to GND with the anode connected
> towards GND.

Is the 2nd resistor connected between to the junction of the collector and
4K7, and goes to the clock input like below?

What value should it be?

I'm guessing the tranny should be a general purpose NPN e.g. 2N3904 or
BC547?

                                         +15V
                                         I
                            -----I4K7I---
                            I
                            I-----IresistorI----- To CLK input
                            I
                            Ic
                           /
INPUT --I 1K I---------(b I )
                I    I     ` e ----GND
                I    I
                I    I
                I    --I1OKI-------GND
                I
                I
                ---- I<------------GND
               diode (anode this side)

Is this right?


> The classic book for CMOS is Don Lancaster's "CMOS Cookbook". Recently
> republished.

Well that's a definite future purchase then :-)

cheers,

Dave