Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
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High Frequency diode - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
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Test & Measurement
Post subject: High Frequency diode Posted: Wed Apr 15, 2009
Joined: Wed Apr 15, 2009 12:58 pm
I am looking for a diode which still functions as a diode
at 100MHz. All diodes that I know have junction capacitance which varies
with voltage. This capacitance makes the diode pass current in both
direction so the diode does not function as a diode any longer. I tried
to cancel out this cap by putting inductor in parallel with the diode
but since the cap varies with the voltage while the inductance value
is fixed, I can't cancel it. Any suggestion is greatly appreciated.
Post subject: Re: High Frequency diodePosted:
Wed Apr 15, 2009 5:24 pm
Joined: Wed Apr 08,
2009 11:07 am
Well, just about any diode on this page
will work like "a diode" at 100 MHz, i.e. it will rectify an RF signal.
http://www.avagotech.com/pages/en/rf_ic ... ace_mount/
you want something that has very little capacitance modulation as the
RF voltage passes by it, there are "PIN Diodes" that have a very thick
middle "I" region, that will not conduct current readily at 100 Mhz,
and will have almost no capacitance modulation.
hsms2802 is an
Post subject: Re: High Frequency diodePosted: Wed Apr 15, 2009 9:10
Joined: Wed Apr 15, 2009 12:58 pm
The simple schematic that I am simulating can be seen below
Please ignore the name "1N4148", I've modified the diode model so
that the Cjo is only 1p
.model 1N4148 D(Is=2.52n Rs=.568 N=1.752
Cjo=1p M=.4 tt=20n Iave=200m Vpk=75 mfg=Motorola type=silicon)
Cjo=1p, however, the diode D1 still passes current in both direction.
Below is the diode D1 current vs. time
Post subject: Re: High Frequency diodePosted: Thu Apr 16, 2009 8:10
Joined: Wed Apr 08, 2009 11:07 am
Did a quick look, and most diode voltge doublers have a DC blocking
cap at the input, as in:
In any event, if you want a diode to operate like
it would in real life, you would need to simulate it like a real-world
circuit. What that means is to have some sort of load impedance, even
if only a megohm or so. You need the capacitors and resistive load to
allow the diodes to attain the proper quiescent DC operating point.
Also, since diodes are pretty much voltage controlled devices (Vd>0.6
volts = conducting, Vc<0.3 volts = not conducting for a junction
diode), I would simulate it all with a 4 volt pk-pk voltage source,
instead of a current source.