Hi, i've seen many different applications and schematics for making Gates from only transistors Does anyone have a schematic or site with a circuit that will work with the least amount of transistors? And also i've seen some use the 2N222 or the BC547 (both are NPN i think), which provides a better 'switching action' and what are the threshold voltages for switching from logic 0-1 and vice-versa?
I really want to know how to make a NOT gate from transistors and if anyone knows about others then it's a bonus for me.
Well, now you're asking for a different beast. A gate circuit (as depicted) is generally expected to respond to a "gross" ( ON or OFF, high or low, 0 or 1) condition. Not a sliding scale signal (like from a sensor).
To achieve a trigger that would "fire" a NOT gate from a sensor you would need, for instance, a voltage comparator (or the like) to give you a distinct, on or off condition within the hysterisis range dictated by the component values you choose for that circuit.
The "V1" is indicating "Voltage Source number 1". The second number is the actual voltage level (Vcc) from V1.
Doesn't really matter so much which Vcc you use, just so long as the output suits, or is designed to be compatible with, the next stage of your circuit.
As for resistor values, since what your most interested in are output voltage level(s), as opposed to a current level, and saturation or complete cutoff of the transistor switch, Vcc levels above, say 9VDC would probably call for increased resistor values (to reduce current). In some more complex NAND gates, resistor values are quite different than those I used.
TTL has levels associated with high and low with a less than X it's a guaranteed low and greater than Y it's a guaranteed high.
CMOS basically has levels too and they are really close to the power supply rails, so that't the idea with a TTL to CMOS converter. Reality just probably means that instead of the output being a totem pole transistor output, it's now a totem pole FET output.
Sure it's possible. Take a look at post #3 in this thread. If you look at the front end of the circuit there is a transistor Schmitt Trigger circuit. If you want that flavor inverted just add another transistor. There are also other variations using transistors. A Google of Inverting Transistor Schmitt Trigger will bring up plenty of examples.