inverting cmos logic signal - Electronic Circuits Projects Diagrams Free

batman · 28th January 2004, 11:34 AM

I posted a while back asking if anyone had an inverter schematic that would make high logic pulses low, and vice versa. I got a response that work when I tested it with just and LED and switching it by tapping the high and low rails, but when I tried implementing it with my logic circuits, it didn't work. The LED I set up to indicate the state was extremely dim with no resistor, and it would not respond to signals I gave it. Is there a particular value of transistor that is appropriate for this task?
thanks

**Nigel Goodwin** · 28th January 2004, 11:57 AM

Quote:

Originally Posted by batman

I posted a while back asking if anyone had an inverter schematic that would make high logic pulses low, and vice versa. I got a response that work when I tested it with just and LED and switching it by tapping the high and low rails, but when I tried implementing it with my logic circuits, it didn't work. The LED I set up to indicate the state was extremely dim with no resistor, and it would not respond to signals I gave it. Is there a particular value of transistor that is appropriate for this task?
thanks

Perhaps you better post the circuit of what you are trying to do?. I'm somewhat concerned about 'The LED I set up to indicate the state was extremely dim with no resistor' - it sounds very much like you are doing something you shouldn't!.

Post the circuit, and let us see what you are doing.

Sebi · 28th January 2004, 02:07 PM

The logic input need logic level, H or L. When the input floating, the CMOS gate can oscillating, and the LED brightness depend from freq. and ratio.

batman · 28th January 2004, 08:26 PM

basically i want to invert the output of a 555 in monostable mode to properly debounce something. the output is high, i need it low.
thanks

Gandledorf · 28th January 2004, 08:28 PM

Maybe I'm missing something obvious, but why not just us a NOT gate, if all we are doing is converting logic levels...

**Nigel Goodwin** · 28th January 2004, 08:42 PM

Quote:

Originally Posted by batman

basically i want to invert the output of a 555 in monostable mode to properly debounce something. the output is high, i need it low.

That's why we need to see the circuit that didn't work, the inverter was quite correct (as you already know, having tested it). So it seems most likely that you were doing something wrong with it - if you show us what you did, we may be able to help.

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28th January 2004, 11:34 AM	(permalink)
batman	inverting cmos logic signal I posted a while back asking if anyone had an inverter schematic that would make high logic pulses low, and vice versa. I got a response that work when I tested it with just and LED and switching it by tapping the high and low rails, but when I tried implementing it with my logic circuits, it didn't work. The LED I set up to indicate the state was extremely dim with no resistor, and it would not respond to signals I gave it. Is there a particular value of transistor that is appropriate for this task? thanks

28th January 2004, 02:07 PM	(permalink)
Sebi	The logic input need logic level, H or L. When the input floating, the CMOS gate can oscillating, and the LED brightness depend from freq. and ratio.

28th January 2004, 08:26 PM	(permalink)
batman	basically i want to invert the output of a 555 in monostable mode to properly debounce something. the output is high, i need it low. thanks

28th January 2004, 08:28 PM	(permalink)
Gandledorf	Maybe I'm missing something obvious, but why not just us a NOT gate, if all we are doing is converting logic levels... __________________ -------------------- -Gandledorf Come visit http://groups.yahoo.com/group/laser_design a group dedicated to help designers build electronic games, and design optical combat systems.