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inverting cmos logic signal

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batman

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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

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batman said:
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

Active Member
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

New Member
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
 

Nigel Goodwin

Super Moderator
Most Helpful Member
batman said:
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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