Rectify 500MHz Small Signal
in [Design]
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From: Jon Slaughter on 25 Sep 2009 19:39 "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in message news:9sqpb5d51gkkqd4jbgdojg7kv44vu8feod(a)4ax.com... > Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude > say 50mV to 500mV peak-to-peak? > > Half wave is OK. > > 1mV accuracy is needed :-( > > Process is X-Fab XB06. > > Thanks! > What about an inverter and adder with nullifier for the negative halves? You could use zero-crossing detection to nullify the appropriate signal. This would be equivalent to inverting the signal during a zero crossing.
From: Jim Thompson on 25 Sep 2009 19:41 On Fri, 25 Sep 2009 13:41:19 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude >> say 50mV to 500mV peak-to-peak? >> > >Only 40dB dynamic range, that's easy. 500MHz is going to be the not so >easy part. > > >> Half wave is OK. >> >> 1mV accuracy is needed :-( >> >> Process is X-Fab XB06. >> > >It's been almost 20 years since I did this (in hardware though) and I >don't know the X-Fab process, but have you thought about successive >detectors similar to what you'd find in a log amp chip? Basically a >bunch of gain stages that each cover a small sliver of the dynamic range >and then saturate, with the grand total being the summed outputs. I'm tending toward AC-coupling plus a DC restorer... to "rectify" ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | LOSE the WUSS BRING BACK BUSH
From: Joerg on 25 Sep 2009 20:06 Jim Thompson wrote: > On Fri, 25 Sep 2009 13:41:19 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude >>> say 50mV to 500mV peak-to-peak? >>> >> Only 40dB dynamic range, that's easy. 500MHz is going to be the not so >> easy part. >> >> >>> Half wave is OK. >>> >>> 1mV accuracy is needed :-( >>> >>> Process is X-Fab XB06. >>> >> It's been almost 20 years since I did this (in hardware though) and I >> don't know the X-Fab process, but have you thought about successive >> detectors similar to what you'd find in a log amp chip? Basically a >> bunch of gain stages that each cover a small sliver of the dynamic range >> and then saturate, with the grand total being the summed outputs. > > I'm tending toward AC-coupling plus a DC restorer... to "rectify" ;-) > Can't use some diode path and servo that against another diode path? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Tim Wescott on 25 Sep 2009 20:24 On Fri, 25 Sep 2009 09:13:53 -0700, Jim Thompson wrote: > Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude > say 50mV to 500mV peak-to-peak? > > Half wave is OK. > > 1mV accuracy is needed :-( > > Process is X-Fab XB06. > > Thanks! > > ...Jim Thompson Make two identical paths, each with a diode, that lets you measure the DC current from the diode to ground. Some fixed amount of forward voltage bias (less than "a diode drop") may be helpful. Drive diode A with your RF, and measure its DC current. Drive diode B with a DC voltage such that its current equals the current in diode A. Measure that there DC voltage. There will be some error because of crest factor, but not (I suspect) enough to worry about. I suspect that this would work just peachy with a pair of unmatched 1N4148s; do it all with a process that lets you match the diodes reasonably well and you should be sitting pretty. .---. | | === | |\ GND '--|+\ ___ | >-------o------o o------|<--o--|___|---o---|-/ | | | |/ | | | ___ | --- '--|___|--|<---' --- | | === GND (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) -- www.wescottdesign.com
From: RST Engineering - JIm on 25 Sep 2009 20:44
You are going to use silicon 1N4148s at 500 MHz. with a 50 mV floor? Jim "Tim Wescott" <tim(a)seemywebsite.com> wrote in message news:-pSdnZPd1p-1wiDXnZ2dnUVZ_jRi4p2d(a)web-ster.com... > > I suspect that this would work just peachy with a pair of unmatched > 1N4148s; do it all with a process that lets you match the diodes > reasonably well and you should be sitting pretty. > > |