Is there a basic circuit that uses the 74LS74 flip flop that I can explore. I just want to understand the basic simulator setup (using 2 units of the 74LS74) and how to apply a digital stimulus and show the output. I see the multi.lib and the dig000_excerpt.lib in the properties of the 74LS74 symbols but dont know if I need to include these libraries in my own project and why. Thanks.
PS I’m particularly interested in using the V7.99 nightly version as it supports V41 of ngspice.
74LS is bipolar low power schottky logic. Do you really want that?
I have not used NGSPICE but I have encountered difficulty in other simulators with trying to include digital ICs in analog circuits. Simply put, I do not think that there are so many analog models out there for digital ICs. I am discussing what used to be called “Small Scale Integration”. Certainly a gate or inverter would be included, and probably a flip flop as well. I have some general interest in this topic.
For example, if you make a simple oscillator with a single schmitt trigger inverter (at least the one that I tried) it turns out to be a power hog, even if the oscillation frequency is low. I think this was a 74HC part. I think the input stage draws high current when the input voltage is in or near the transition zone. I have such an oscillator on a test board, and it draws 15 - 20 mA when running on 5V. That power level will not fry an egg, but it will cause a SOT-23 chip to run noticeably warm and is probably not a good design just for that reason alone.
Here is an example circuit. PortusHaywoodDecoder_Divider.kicad_sch (64.6 KB)
I’m using 7.99 nightly version and the schematic is imported from Altium designer.
I’ve not made any attempts to set the schematic up for any simulation yet as It took me a while to just do the schematic in Altium. The actual import into kicad was trouble free.
Thanks.
Why is it horrible? How can it be improved? I’m only interested in how ngspice can be used to simulate a d type flip flop. A 74HC74 can easily be substituted in the REAL circuit if it can be of benefit. It’s used in this context. PortusHaywoodForQSPICE.pdf (194.8 KB)
I have a question, I need a FlipFlop (not a 74LS74 (the cd4013)) which is essentially identical to yours but instead of having reverse Set and Reset they are normal, that means at low, they allow data to write to click, and at high, they activate the set and reset functionality.
I wanted to see if it was within my abilities to edit this simple thing.
Which is quite a mouthful but I have no idea how to invert these (besides using a cmos inverter but that is overkill)
Edit: Under closer inspection it seems set and reset are not implemented for 74HC74, anyway. Which is a shame because I wanted to simulate a circuit that implements this functionality