Schmitt Triggers

[satindas]

Hi,

New here and (fairly new) to electronics design in general so please be gentle

I'm trying to build a synthesizer circuit which takes regular 5V gates as inputs and feeds them to some CD4000 series logic IC's for mangling.
At the front end I'm using discrete schmitt triggers to provide the correct levels for the CMOS but with four gate inputs that's 8 trannys,12 resistors and a few diodes for neg volt protection. Is there a better/more efficient way (op amp buffer ?) to get my 5V gates to drive the CMOS correctly.
Many Thanks .

 

[4pyros]

Do you have a drawing of what you are trying to do now?

 

[satindas]

Hi 4pyros,
this is just the input section... if I zoom out more to include the whole schematic it becomes pretty unreadable but I've got it breadboarded and it all seems to work fine. It basically alternates the input gates between two outputs using a 4013 and a 4066

 

[KeepItSimpleStupid]

You might just use a level shifter like a CD4504B: https://www.google.com/url?sa=t&rct...9Q3RMqoSHjy_atQ&bvm=bv.67720277,d.cWc&cad=rja

 

[4pyros]

Or the CD4096.
There are many, look up TTL to CMOS buffer chip.

 

[Reloadron]

What your drawing represents I believe is a Schmitt Trigger front end using discreet components. As drawn with the values you are using the output of transistor Q3 will swing positive when the input signal threshold crosses right around ~2.64 Volts. You mention needing 4 channels.

In keeping it simple for 4 channels why not use a simple LM339 quad comparator? Your input signal would go to a positive input and the negative input would go to Vreference (2.64 volts) and a simple 10 turn pot could be used to adjust and set your Vreference. It seems all you are concerned with is triggering at some preset input level. If I read this correctly a LM339 quad comparator could manage all 4 channels on a single small chip with a small handful of resistors. I wouldn't get to hung up with the TTL level to CMOS level thing. I can make a cartoon if it would help but what I am thinking **broken link removed**

Ron

 

[4pyros]

Here is some more reading for you;