I did some quick LtSpice simulations of the Adcom GFA-555 and am making the asc file available here. I was in a rush used good Fairchild transistors for all the small signal devices and plan to substitute correct models as I find them. Used andy_c's output models which are probably much faster but will do for now - thanks andy! This file has SPICE directives to provide analysis of the distortion; use "view" "spice error-log" to see the results.
Remove .txt from the file names to use them with LtSpice.
I quickly collected some models that I had on this system, my main LTSpice install is on another system. These models are in the attached .LIB file. I have many models but probably not for the remaining transistors so if anyone has them please post them, especially looking for the correct outputs.
Remove .txt from the file names to use them with LtSpice.
I quickly collected some models that I had on this system, my main LTSpice install is on another system. These models are in the attached .LIB file. I have many models but probably not for the remaining transistors so if anyone has them please post them, especially looking for the correct outputs.
Thanks Pete got it running in time domain.
I'm working on closed loop Bode plots at the moment
I'm working on closed loop Bode plots at the moment
Last edited:
PS caps got in there as 100,000uF should be 15,000uF.
You just uncomment the .ac spice directive, or are you already an LTspice user?
You just uncomment the .ac spice directive, or are you already an LTspice user?
Is there a resistor missing?
I notice that only Q1 has an emitter resistor, but not Q2? Is this the way the design is, or is there an omission?
I notice that only Q1 has an emitter resistor, but not Q2? Is this the way the design is, or is there an omission?
got closed loop bode plot working fine
having trouble breaking the loop for open loop shows neg gain. LOL
having trouble breaking the loop for open loop shows neg gain. LOL
I believe that there is an example in the audio amp tutorial LTspice file. Comes with the installation. I don't think it uses any of the advanced methods. There is a "loop probe" that is probably more accurate discussed here, see andy's post #29:
http://www.diyaudio.com/forums/solid-state/144719-open-loop-gain-phase-margin-etc-3.html#post1839758
and here:
http://www.diyaudio.com/forums/software-tools/101810-spice-simulation-86.html#post1793923
Are you a member of the Yahoo LtSpice user's group?
http://www.diyaudio.com/forums/solid-state/144719-open-loop-gain-phase-margin-etc-3.html#post1839758
and here:
http://www.diyaudio.com/forums/software-tools/101810-spice-simulation-86.html#post1793923
Are you a member of the Yahoo LtSpice user's group?
Hi Pete,
I wish I had the time to learn how to use spice. It's great that you can.
-Chris
Yes, it was. I'll back you up on that.
I wish I had the time to learn how to use spice. It's great that you can.
-Chris
Updated .asc file, fixed supply caps, and added SPICE directives to turn off compression for distortion measurements.
Did you try LTSpice Chris? You should there is an amp example included and this file should also run just fine.
Hi Pete,
I did download it a while ago now. I haven't had a chance to even run the install yet. Just as well since the copy I have is now out of date, and my hard drive went from 130 GB free to about 3 point some odd GB free. The 'puter doesn't recognize the larger HD either, so I am forced to move over to a newer machine running Lunix instead of XP. I can't afford to buy yet another license from u$oft because the MD is different.
Once I get computers figured out again, I will do an install and try to learn how to use it. One thing that is a real drag is that I have to do schematic capture twice. One for the simulator, and one for the PCB layout program.
I really appreciate your help Pete, thank you. I have failed you completely though, by not having the program installed yet. Our younger members will be teaching me next!
-Chris
I did download it a while ago now. I haven't had a chance to even run the install yet. Just as well since the copy I have is now out of date, and my hard drive went from 130 GB free to about 3 point some odd GB free. The 'puter doesn't recognize the larger HD either, so I am forced to move over to a newer machine running Lunix instead of XP. I can't afford to buy yet another license from u$oft because the MD is different.
Once I get computers figured out again, I will do an install and try to learn how to use it. One thing that is a real drag is that I have to do schematic capture twice. One for the simulator, and one for the PCB layout program.
I really appreciate your help Pete, thank you. I have failed you completely though, by not having the program installed yet. Our younger members will be teaching me next!
-Chris
Since I am still mainly lurking and trying to learn I figure maybe I'll offer my assistance to help you out with your computer problem...if you need/want my help just PM me. While I am a Materials Scientist/Chemist, I have moon lighted as a sys admin for an office in the past.
As for LTSpice, I have been using it a lot to teach myself electronics and theory. It wasn't until really playing around with LTSpice that I understood things like FlipFlops, Logic Gates, etc. (I understood the concept but didn't understand their power).
As for LTSpice, I have been using it a lot to teach myself electronics and theory. It wasn't until really playing around with LTSpice that I understood things like FlipFlops, Logic Gates, etc. (I understood the concept but didn't understand their power).
Last edited:
Hello
I was using Tina as a simulator but now I use LTspice who are much better in distortions analysis, and wen you have good spice models the LTspice simulations are quite close to a real amps, the amps prototypes I've done was very close to the simulation.
Bye
Gaetan
I was using Tina as a simulator but now I use LTspice who are much better in distortions analysis, and wen you have good spice models the LTspice simulations are quite close to a real amps, the amps prototypes I've done was very close to the simulation.
Bye
Gaetan
Last edited:
GFA-555 Loop Gain Av*B
1st zero due to C3 and R5 47uF & 1K
1st pole due to C2 miller cap
2nd zero due to C4 to inverting input
1st zero due to C3 and R5 47uF & 1K
1st pole due to C2 miller cap
2nd zero due to C4 to inverting input
Attachments
Last edited: