Hi Alberto, I've seen that switch, and it looks like the dead short or the 50 ohm termination is a problem. Since the switch does not present a high impedance during the time it's open, there is no way to avoid having it discharge (or drain) the integrating caps, so they can't function as a sample and hold.
Also notice that the turn on vs turn off time varies, it turns on in 3.6 nS and it turns off in 5.8nS. This isn't going to work well since 1 cycle of 144 MHz is 7 nS. While the switch passes 144 MHz, it won't turn on and turn off fast enough to be usable at 144 MHz. IF (and it's a big IF) we could slow down the on time transition, it might be usable. If it would turn on in 5.8 nS and turn off in 5.8 nS, it would be good, provided the other switches could operate with the same on and off times (switching times are all consistent). I've chatted with AD about these issues, there is no way to burn out the 50 ohm resistors to effectively remove them from the circuit. There is no comparable analog switch made by them that does function properly (for us). They are NOT planning or designing a suitable switch. I talked to a friend who designs cmos about the consistency problem. It is a relatively simple task to equalize the switching times IF 'adjustability' is a design goal. But, it is very expensive to make the masks necessary to do the fabrication of the parts. Without a major demand for switches with consistent (equalized) on/off times, a suitable switch will never be built. I have some ideas about how to control the switching speeds and would love to chat with anyone interested in QSD at vhf. Talk to me off list, as the subject might be off topic for this group. Art At 06:13 AM 10/23/2005, you wrote: >I know that a few of you are considering the idea of building a QSD >directly at 144 MHz. I have just received an Analog Device bullettin >with the specs of a new high speed analog switch. > >Maybe it is worth investigating its suitability for that application. > >http://www.analog.com/UploadedFiles/Data_Sheets/847169922ADG901_2_b.pdf > >73 Alberto I2PHD > > > > > > >Yahoo! Groups Links > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
