Hi All, I would like to rectify a signal with peak voltages in the range of
50mV to 100mV. Are there any diodes that will start to conduct in this voltage range? Any other options besides a diode, I need it to be a passive device. Thanks, James
I would say you need to abandon the idea of doing this "on the cheap" with a passive setup.
Even though you seem to class diodes as active components, I don't know of any that will conduct this low - let alone what you are going to do with the signal once you have removed the diode "voltage". Chances are anything that will is gonna be mil-spec and/or hideously expensive/unobtainable. Germanium stuff can come down as low as 180mv but this is still way over what you are after.
google "precision rectifier" there's plenty out there and depending on the opamp, they can work in this formation (i.e as a rectifier) down to a few micro-volts (some even lower)
the first thing that came up for me here was
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which gives a nice precision full wave rectifier circuit which you could construct for
further browsing turned up this very concise little page on precision rectifiers with single opamps which further reduces your cost/complexity.
hant tried any of these - experienced eyes in this group will no doubt be able to comment on particular solutions to greater improve everyone's knowledge... gentlmen; the floor is yours.
"no forward tunnel current" is not exactly correct. A back diode is a tunnel diode with a low Ip.
Several people still make back diodes. They are photolithographically fabbed on germanium, unlike the classic/horrible tunnel diode fab. Back diodes are still the lowest noise unbiased RF detectors.
look at this mine first upper schematics (slide C); it is a 70Khz IF amp for measuring signal strenght. (for TDA7000 IC)
Last half of the schematic- passive part at the end: The right last 2 resistors provide current biasing two germanium point glass demodulator type diodes to the knee of conducting signal .. So, you can measure from few mV & up to 2V RMS signals..
*ALL* diodes are passive. THe "backwards diode" is an Esaki diode with Ip=Iv; net effect is good rectification in the reverse (backwards) bias and a "breakdown" in the region of 350+mV.
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