The original ASCII schematic has an error if a monospaced
font is used. The Switch to ground should be BETWEEN the
two "X" marks. I added a + where it should connect.
Otherwise the comment about not shorting the output
is invalid.

Robert

Tal 012 wrote:

> Thanks guys for you advices!
> 
> Tal
> 
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Russell McMahon
> Sent: Thursday, October 21, 2004 12:53 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] 4066 bilateral switch leak??
> 
> 
> 
> The impedance of an "off'" 4066 switch is high but finite. This impedance
> forms a voltage divider with the output impedance and you will get some
> output. Capacitive coupling may also provide some signal path.
> 
> 1.    Using a lower output impedance will help
> 
> 2.    You can get a much better reduction by connecting a second set of
> 4066's which ground the outputs when the inputs are turned off. This is not
> a suitable solution if the outputs have some other signals on them as well
> when they are turned off but is a good solution when the output has no other
> signal source.
> 
> 3.    A solution that works in all cases has THREE 4066's per channel!
> 
> 
>         INPUT ---X-----+-------X-------- Output
>                        |
>                        *
>                        |
>                     Ground
> 
> 
> Switches X are turned on when output is required.
> Switch * is turned on when the output is not required.
> This does not ground output or input but does ground the signal path.
> It works well.but takes three times as many gates.
> 
> 
> 
>         RM
> 
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