hahaha, 300mohm. I think you could achieve that maybe by putting two leads in a glass tube full of air!
Sorry about that. However, I doubt a 300mohm resistor, you could change the resistance probably by blowing on it. And really put it out by barely touching the leads
lol This is a bit of sarcasm, however, I think Jean-Paul is probably right
Sorry about that. However, I doubt a 300mohm resistor, you could change the resistance probably by blowing on it. And really put it out by barely touching the leads
lol This is a bit of sarcasm, however, I think Jean-Paul is probably right
Lol, yes, there's a common misconception; that little resistance, for some reason, is a very high value.
I'll just settle with almost no conductance, or transconductance if you prefer. Yes, very very high resistance.
But either way, this great thing in the brain is so nice to automatically fix grammar before it is noticed consciousely.
It can be troubling sometimes when one can read over and over a statement that really makes sense, but not grammatically. Darnit
I'll just settle with almost no conductance, or transconductance if you prefer. Yes, very very high resistance.
But either way, this great thing in the brain is so nice to automatically fix grammar before it is noticed consciousely.
It can be troubling sometimes when one can read over and over a statement that really makes sense, but not grammatically. Darnit
Nope, it's the bias resistor directly on the electret capsule and it wants to be as big as possible, it overranges all my handhelds (time for the Keithley). I've used 10,000Meg resistors to measure the bias current on 20 fAmp opamps. Dick Burwen used 1000Meg in his mics and I think John Curl advised B&K to put even bigger ones in theirs. Those little Panasonic capsules actually let the gate float until the drain-souce leakage just balances the gate-source forward bias (just barely in enhancement), clever trick but lousy for dynamic range. A great interview question is to take one of these appart and ask someone how it works, since it appears to be only a FET and nothing else (I stumped Bob Pease with this one).
Scott:
In the US, Caddock <http://www.caddock.com/> makes a high-voltage "MG" resistor that goes all the way up to 10,000Mohms. OTOH, I think that the physical package could be fairly large. Don't know for sure, as I haven't used the high-value MG's myself. In a smaller physical package, Caddock's TF series goes up to 125Mohm, and their MK632 and MK620 go up to 100Mohm.
As an aside, when I was at one of my favorite component retailers today, I happened to notice some 500Mohm and 1Gohm(!) resistors in stock, in what I think were 1/4W packages. I asked the proprieter about them, and he said that every now and then someone would buy a few.
I didn't look at the lower values, but I'd be surprised if there weren't some 300Mohm resistors in stock, too. I'm in Tokyo, but if you can't find the resistors locally, I'll pick up some the next time I visit that retailer and post them to you.
hth, jonathan carr
In the US, Caddock <http://www.caddock.com/> makes a high-voltage "MG" resistor that goes all the way up to 10,000Mohms. OTOH, I think that the physical package could be fairly large. Don't know for sure, as I haven't used the high-value MG's myself. In a smaller physical package, Caddock's TF series goes up to 125Mohm, and their MK632 and MK620 go up to 100Mohm.
As an aside, when I was at one of my favorite component retailers today, I happened to notice some 500Mohm and 1Gohm(!) resistors in stock, in what I think were 1/4W packages. I asked the proprieter about them, and he said that every now and then someone would buy a few.
I didn't look at the lower values, but I'd be surprised if there weren't some 300Mohm resistors in stock, too. I'm in Tokyo, but if you can't find the resistors locally, I'll pick up some the next time I visit that retailer and post them to you.
hth, jonathan carr
Of course, if you bootstrap the gate bias resistor, you can make it look much higher in value. Some of the trickier condenser microphone circuits not only bootstrapped the gate resistor but also the drain of the input FET (to reduce input capacitance). Are you doing this with silicon or valves?
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