Logic IC's from transistors...

[N.Carsane]

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.

Thanks in advance!

 

[cowboybob]

Doesn't get much simpler than this:
Ooops.. Wait one...

 

[N.Carsane]

Doesn't get much simpler than this

If i were to use an input from a sensor that varies...what would be the switching threshold?

 

[cowboybob]

If i were to use an input from a sensor that varies...what would be the switching threshold?

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.

 

[N.Carsane]

Thanks and are there any other gates that can be made from transistors like the AND and the OR gates and a NAND GATE (in their simplest form please)?

 

[cowboybob]

Thanks and are there any other gates that can be made from transistors like the AND and the OR gates and a NAND GATE (in their simplest form please)?

AND gate:

OR gate:

NAND gate:

Google "(GATE type)" transistor gate circuits: there are scads of examples...

 

[N.Carsane]

Thanks!

 

[KeepItSimpleStupid]

Then you can build all the other logic functions from NAND or NOR gates.

e.g A NAND with one input is a NOT gate.

You can do some research on RTL, DTL, and TTL logic families: https://en.wikipedia.org/wiki/Logic_family

PS: Nice job CBB

 

[cowboybob]

Thanks, KISS (and all of you who gave me a like). That means a lot to me, coming from ya'll...

 

[N.Carsane]

The images show 15V/11V, but would it work with 5V or 9V or will i have to change the resistor values to make it work?

 

[cowboybob]

The images show 15V/11V, but would it work with 5V or 9V or will i have to change the resistor values to make it work?

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.

 

[KeepItSimpleStupid]

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.

 

[eTech]

Thanks and are there any other gates that can be made from transistors like the AND and the OR gates and a NAND GATE (in their simplest form please)?

Hi

There is an excellent book on creating logic from transistors.

Its an oldie, but a goodie..

Google for "RTL Cookbook" by Don Lancaster

eT

 

[N.Carsane]

Hi

There is an excellent book on creating logic from transistors.

Its an oldie, but a goodie..

Google for "RTL Cookbook" by Don Lancaster

eT

Is this it? https://www.tinaja.com/ebooks/rtlcb.pdf

 

[KeepItSimpleStupid]

Yep, and that's Don's website.

 

[N.Carsane]

Thinking about gates, is it possible to make a schmitt inverter with transistors although i doubt you can...

 

[eTech]

Thinking about gates, is it possible to make a schmitt inverter with transistors although i doubt you can...

You can lead a horse to water...but you can't makem' drink...

See page 81 of the RTL Cookbook..

eT

 

[atferrari]

Hi

There is an excellent book on creating logic from transistors.

Its an oldie, but a goodie..

Google for "RTL Cookbook" by Don Lancaster

eT

I bought his "TTL Cookbook" about 25++ years ago. I did not know there was one about RTL!

 

[4pyros]

The RTL Cook Book.... an oldie but goodie.
Some times if you only need one gate its fine.

 

[Reloadron]

Thinking about gates, is it possible to make a schmitt inverter with transistors although i doubt you can...

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.

Ron