1-bit NOT gate circuit required.

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pkshima

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Hi,
I need to invert/NOT one bit. Unfortunately, The NOT gates ICs available are HEX NOT gates i.e. 6 NOT gates in a chip. Using this IC takes up more space on my board than I would like to spare it.

I would like something smaller and simpler.
I am sure there would be a simpler way to convert a 1 to 0 and vice-versa.

Thanks in advance
 
use a SOT23 NPN BJT or N-Type FET,

these act as inverters IF wired up as common-emitter with a collector/drain resistor
 
thanks styx. M not much of an electronics person so any idea if it will work fine as it is or will it require components for biasing it. will the input, outputs be compatible with CMOS levels ?
 

I know for a fact that you can make a NOT gate with one BJT NPN transistor. I think you connect the collector to +ve, the base to input and the emitter to output. I'm not exactly sure about the connections, but it can be done with one or two transistors.
 
Hi Pradeep,
You can't use a JFET, because it would never turn-off. If you use an NPN transistor, it would need a base resistor and a collector resistor. A 2N7000 enhancement-mode Mosfet would work, it comes in a regular little transistor package and a surface-mount one too, and needs only a drain resistor to be a logic inverter:
 

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NO! - that wouldn't invert it.

Use an NPN transistor, connect the emitter to 0V, and the collector through a resistor (pullup resistor) to 5V, take the output from the collector. The input is fed in the base via a series resistor.

Here are circuits using both NPN and PNP that I posted previously
 
NO! - that wouldn't invert it.

I used the words "I think" and "I'm not exactly sure about the connections". I wasn't definite about the connections I stated, but I know that an NPN will work. Follow Nigel's steps for the connections.
 
Thank you all for your replies

So I guess using a NPN BJT is the simplest way out. can anyone suggest which one i should use i have 2N3904/BC548/SL100/2N2222 ? or anyone else. Its been ages since I knew calculating the base/collector resistor values from the alpha/beta/gamma of the BJT so can someone suggest the resistor values as well :wink:

thanks again
 

Any small NPN will be fine, from the choices you've given I'd use the BC548, simply because it's a European device.

Resistor values are not at all critical, try 10K for each one!.
 
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