Edge triggered DFF

Thread Starter

Faizan Ahmad

Joined Mar 6, 2016
9
I want to make an edge triggered DFF using LTspice.
Tried to build a latch , I am getting spikes at the output.
If somebody could help me with that.

attaching the file
 

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WBahn

Joined Mar 31, 2012
24,974
If you would, take a screen shot of your circuit schematic, save it as a reasonably sized PNG file, and post it. That will allow more people to look it over. You might also post your sim results showing the spikes you are talking about.
 

WBahn

Joined Mar 31, 2012
24,974
It's likely that the cause of the spikes is charge injection due to too fast rise and fall times combined with using an ideal pulse source that can source/sink unlimited current.

Take your two pulse sources and run them through inverters (or a pair of inverters if you don't want to deal with the signal inversion) similar to how you derived clkb. That will give you realistic rise and fall times and drive strengths.
 

Thread Starter

Faizan Ahmad

Joined Mar 6, 2016
9
20160326185711.jpg
It's likely that the cause of the spikes is charge injection due to too fast rise and fall times combined with using an ideal pulse source that can source/sink unlimited current.

Take your two pulse sources and run them through inverters (or a pair of inverters if you don't want to deal with the signal inversion) similar to how you derived clkb. That will give you realistic rise and fall times and drive strengths.


Thanks the spikes are gone.

next is this what I want to do , I copied the circuit to make a slave ckt. , Is that right
 

WBahn

Joined Mar 31, 2012
24,974
Depends on what you are looking to achieve. Do you want the data to be edge-sensitive on one edge but the output to change on the other edge? Or do you want the output to change on the same edge?
 

Thread Starter

Faizan Ahmad

Joined Mar 6, 2016
9
Depends on what you are looking to achieve. Do you want the data to be edge-sensitive on one edge but the output to change on the other edge? Or do you want the output to change on the same edge?

I want the output to change on the same edge
 

Bordodynov

Joined May 20, 2015
2,455
Spike appear due to the fact that the parasitic capacitance does not take into account the source and drain. You can simply get rid of the spike using in Scheme following: .option cshunt=1f.
This will add the specific capacity to each point of the circuit.
 
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