Message	Date	From	Subject
8759	2013-06-26 15:27:29	Jim Miller	View distortion in LTSpice?
I'm trying to figure out how to observe the output in the frequency domain in hopes of seeing what sort of higher order products might be being produced when fed with a single frequency sine wave. I'm looking for crossover distortion. Anyone know if this is possible in LTSpice? Thanks jim [Non-text portions of this message have been removed]
8760	2013-06-26 16:24:46	Jim Miller	Re: View distortion in LTSpice?
Found it via google. Also some good options. .options numdigit=7 ; will force double precision for good low level distortion measurements .options plotwinsize=0; will disable compression which is lossy I combined it with 10nsec samples which take a long time but I get a nice clean input trace which allows me to really see what the output is doing. FWIW output 2nd harmonic is down 90db and 3rd is down about 84db which isn't a bad start. FWIW, I'm working through a simulation of Chris Trask's paper titled Push Pull Amplifiers for Active Antennas. http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf Right now I have the differential buffer stage made up with 2907 and 2222 and the output the same. Next step is to change the output transistors to BFQ19 and BFQ149. I'll play with drive levels more when I get those in place to see what improvements I can make. If anyone is interested I'll post the LTSpice schematics as I go. jim

Found it via google. Also some good options.

.options numdigit=7 ; will force double precision for good low level
distortion measurements
.options plotwinsize=0; will disable compression which is lossy

I combined it with 10nsec samples which take a long time but I get a nice
clean input trace which allows me to really see what the output is doing.
FWIW output 2nd harmonic is down 90db and 3rd is down about 84db which
isn't a bad start.

FWIW, I'm working through a simulation of Chris Trask's paper titled Push
Pull Amplifiers for Active Antennas.

http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf

Right now I have the differential buffer stage made up with 2907 and 2222
and the output the same. Next step is to change the output transistors to
BFQ19 and BFQ149. I'll play with drive levels more when I get those in
place to see what improvements I can make.

If anyone is interested I'll post the LTSpice schematics as I go.

jim