[sdiy] trouble driving cmos from modular signals

[Tom Wiltshire]

Richie is quite right - a capacitor, not a diode. Much more sensible to AC couple the signal in.

10K/10K might work for the divider, but ti depends where the switching levels are. I'd probably start with a pot and tweak it to see if you can get anything happening, and then measure the values that work.

Good luck!

T.

On 14 Sep 2012, at 16:20, rburnett at richieburnett.co.uk wrote:

> I think maybe he meant to AC couple the signal into the mid-point of the potential divider with a CAPACITOR rather than a DIODE ????
> 
> -Richie,
> 
> 
> 
> On 2012-09-14 16:08, Dan Snazelle wrote:
>> Sent from my iPhone
>> 
>> On Sep 14, 2012, at 7:26 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
>> 
>>> 
>>> Peter could well be right about it being speed not levels that is causing the problem.
>>> 
>>> However, if it were levels, you might be able to make it work by putting a voltage divider between the rails on the input, and then feeding that with a diode - biasing the input to a midpoint value essentially. It's dirty but it can work, especially on 4000 series CMOS.
>>> 
>>> HTH,
>>> Tom
>>