Dan, Sorry for the late reply; I've been in Singapore. There is a new page with good hyperlinked indexes of all the files in the LTSpice Forum. There's a link on the home page that says, "Hyperlinked lists of all uploaded files and links can be found in Files/ToC.". The URL is
http://tech.groups.yahoo.com/group/LTspice/files/%20%20Tables%20of%20Contents/ The 74HC and HCT libraries are in their own subdirectories under: Files > Lib. There's a help file that tells you how to install the library. In-summary: 1. All the 74HCXX.asy files go into a folder: C:\Program Files\LTC\SwCADIII\lib\sym\Digital\74HC 2. The single 74HC.lib file goes into the folder: C:\Program Files\LTC\SwCADIII\lib\sub 3. Restart LTSpice, your new parts now appear under Digital > 74HC. Above assumes you have installed LTSpice to the default location in Program Files. Regards, David --- In [email protected], "Daniel Jackson" <[EMAIL PROTECTED]> wrote: > > David > > I am interested in the 74HC files from LTspice group, I would go and > do a search, but I know how many of them files Helmut has now. And > all of them file folders he has there to sift through. If you get a > chance upload some on a zip in the Spice folder in the files here and > we all will get to looking into the Dual D flip flop ideas and > problems. Well, so long as it isn't something massive that Helmut > compiled. And would take you allot of uploading time and waiting. > > If you get that simulation running right, then it would make a good > thing to add to the group files. Others could help you out if you hit > a snag with it. > > Semi working models are ok I think, someone can work them on up. > Well, as long as it is not something super secret you are working on. > > Dan > > > --- In [email protected], "drmail377" <drmail377@> wrote: > > > > I've simulated the Tayloe integrator in LTSpice - sort of. I simulated > > the circuit in "Part-I of SDR for the Masses" using Helmut's 74HC > > library for the logic chips with the voltage controlled switch devices > > forming the heart of the FET multiplexer. The switching stuff works > > ok, but the simulation is so slow, and has to run so long in order to > > see something at baseband; it's just not practical. > > > > I'm going to give it another try, this time I'll eliminate the 74HC > > devices as they may be causing a lot of the slow-down. I'll replace > > them with voltage pulse sources at the switch control inputs. I might > > also do with some deeper optimization as well. I'm simulating in WinXP > > SP2+ on a 3.2GHz Prescott with 2GB of RAM. > > > > Regards, David > > > > --- In [email protected], "Daniel Jackson" <wavelengths@> > > wrote: > > > > > > I was thinking today of the Taylor circuit also. As Cecil says, > > > sometimes the simulations can run slow. But if you got a 2.4 GHz > > > processor it might not take too long. My processor is not that fast. > > > > > > I am seeing that simulation times from 4.5u to 200u appear to show me > > > most of what I need to see. > > > > > > Also, I can see that the idea of a switching mode mixer seems to be > > > better in broadband HF use than the analog biased circuit is. When > > > there is no agc control voltage to control the gain. > > > > > > The switching mixer seems to have a set level of input that does not > > > vary in input amplitude over the range of the spectrum and hence does > > > not result in a high level input on low frequencies and low levels on > > > higher. Which imbalance analog mixers if there is no agc used. > > > > > > So circuit ideas such as I am trying have to be moved from the analog > > > to switcher versions for completing the picture I think. > > > > > > We all should try to simulate the Tayloe circuit as an educational > > thing. > > > > > > Dan > > > > > > --- In [email protected], k5nwa <k5nwa@> wrote: > > > > > > > > At 08:24 AM 2/28/2008, you wrote: > > > > > > > > >Hi Dan, > > > > > > > > > >I would like to simulate a Tayloe mixer using a quad bi-lateral > > > > >switch, e.g., 74XX4066 and/or 74CBT3253 etc. I have a working > > > > >schematic in LT, but as I suspected, the simulation would take > years > > > > >to provide reasonable data at the I-Q output, it's just too slow > > given > > > > >the input vs. output frequencies. > > > > > > > > > >Anyway, I'd like to discuss this with you off-Forum, May I? > > > > > > > > > >Thanks, David > > > > > > > > > > > > > I use LTspice and it just takes a few seconds to simulate through > > > > several cycles of output. > > > > > > > > On the simulation is the clock and Quadrature generating circuitry, > > > > the switches, and the output op-amps, basically an equivalent to a > > > > SoftRock and it just takes a few seconds on my PC to run through a > > > > simulation of 200 uS. > > > > > > > > For the switches I use a sub-circuit to emulate the properties > of the > > > > FT switches which are shown below, so it doesn't look like the > actual > > > > switch but it behaves like the actual switch; > > > > > > > > 1. Has a finite resistance > > > > 2. Make before break > > > > 3. The switch turns 90% on in the first ns, and fully on in a > > > > exponential rate for the turn on time. > > > > 4. The switch turns 90% off in the first ns and its exponential for > > > > the turn off time until it hits 100% > > > > > > > > It's main element is a voltage controlled resistor, with RC > circuits > > > > used to shape the waveform fed to the resistor so it has the proper > > > > turn on rates. That is a generation 2 switch, the latest is > > > > generation 4 but I seem to have lost it along with version 3, it > > > > physically implements a real switch with all it's warts, > somewhere I > > > > have to have a copy of it but I have no clue where. > > > > > > > > > > > > Cecil > > > > K5NWA > > > > www.softrockradio.org www.qrpradio.com > > > > > > > > "Blessed are the cracked, for they shall let in the light." > > > > > > > > > >
