On 6/7/06, Peter wrote: > > On Mon, 5 Jun 2006, Edward Cooper wrote: > > > Hi all > > > > Anyone got any suggestions as to how to put together a 5MHz sawtooth > > generator, I'd really like something quite linear and adjustable if possible, > > can't see any simple chip solutions out there so looking for a bit of advice. > > > > Its for playing with a FMCW radar module if anyone is interested > > I have done this, almost for the same purpose. Many better opamps can > generate a triangular waveform at 5MHz with very good linearity using a > standard schematic. Use a small R so the C can be relatively large (this > requires an opamp with some power bandwidth). You probably want a > triangular waveform (not sawtooth) for FMCW. That is what I used. Even a > venerable uA733 can do this quite well. A more modern device would be > from National or Maxim, e.g.: > > http://www.national.com/pf/LM/LMH6732.html Peter, it looks like this one has a variable bandwith between 50-540MHz. Have you tried to use it as a controlled LPF ? The guys from National claimed 1.5GHz BWT at -3dB, did you check that ? I must order one... BTW, it's too good for a 5MHz sawtooth... thx, Vasile > > The app. notes are also worth reading, esp. OA-15, OA-30 and OA-31 . A > schematic for a sawtooth generator using a current controlled opamp can > be found in the LM3900 datasheet, among other places. > > Note that it is dead easy to make one of these oscillate, the wiring > layout must be VHF at least. No flying pigtails here. By the way the > LMH6732 has almost unbelievable performance imho. 1nV/sqrt(Hz) at 100kHz > and 3mA bias ?! > > hope this helps, > Peter > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist