[sdiy] Switching large analog signals from lower voltage logic

[Dave Manley]

On 4/26/2011 7:00 PM, Olivier Gillet wrote:
> Hi all,
>
> I need to switch/mux analog signals in the 0-9V range from logic
> signals generated by a microcontroller powered at +5V. Do you know any
> part which could deal with the lower logic level? I've tried with some
> 74hc4051s, it somehow worked, but the datasheet mentions a threshold
> of 4.7V (up to 6.3V) under 9V operation, so I suspect this could be
> very flaky. I'm not too fond of doing level translation for this, but
> if this is the way to go...

Idea which I haven't tried but should work:

 From the micro output put two resistors in series to +9V, connect the
cmos control input to the middle of the two resistors:

Micro output---R1---+---R2----+9V
                     |
                     |
                     CMOS Input

Try something like R1=10K, R2>=20K.

-Dave