Not necessarily for TTL, yet for a digital signal: how would you invert the signal: using a BJT or a MOSFET?
Answers written behind your questions.Need more information:
What is the amplitude of the input signal? depends on application, but mostly 12V
Where do you want the trip point to be? ~Half of the input amplitude? it's square wave, so halfway surely would do
How much delay can you tolerate? does not matter, frequency <200Hz
Does the delay from rising edge of input to falling output have to be the same as going the other way? does not matter
What does the output have to drive? Source current same as Sink current? source = sink, impedance about 100Ohm
What is the power supply voltage used on the output side? 12V
Are you simultaneously require level shifting from input to output? I do not understand?
Go aheadI could come up with about 20 more...
The reason I prefer MOSFET is that it is easier to driveI find it most easy using pull-up resistors and bjt's, mosfet works as well. For TTL's be aware that many of the old circuits have open collector output and input will be regarded as high if not connected (not recommended).
I do too because no gate resistor needed like the base resistor in a BJT.
Hardly puts the trip point halfway between 0V and 12V so has crummy noise immunity. With an NPN, it starts turning on at about 1V unless you create a two resistor voltage divider. Same with an NFET except that it begins to turn on at Vth and the resistors can have higher resistance...
thanks, that I do understand.To invert a 12 V signal and produce another 12 V signal, you will get more consistant performance with a BJT and a zener diode than with a MOSFET, meaning a more predictable trip point with less drift due to temperature changes and better repeatability from one component to another.
And what if the trip point does not matter, as in a simple low frequency circuit (less than 200Hz)?To invert a 12 V signal and produce another 12 V signal, you will get more consistant performance with a BJT and a zener diode than with a MOSFET, meaning a more predictable trip point with less drift due to temperature changes and better repeatability from one component to another.
Sorry, that post seemed a little incomprehensible to me. Sort of like it was typed on a phone.
The load (in my case here) is high impedance.Harkens back to day of RTL.
About your current sink, current source requirement? Do you mean you want a single circuit that can both source 12V/100Ω = 120ma and sink 120mA. Or do you mean that sometimes you would like to source 120mA into a grounded load (using circuit A) and other times you would like the circuit to sink 120mA from a load returned to +12V, and you would be willing to change (to circuit B) depending on the nature of the load?
Ah, I see. THat clears things up.That's ok. English is not my native language...
Here is a picture that has serious problems. V(out1) vs V(in) at three different values of load resistance.
Note the skewed threshold.
Note the output voltage when the load is 100Ω.
Note the power dissipation in R1.
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