Re: PAD5
- From: Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx>
- Date: Sat, 02 May 2009 11:11:28 -0700
John Larkin wrote:
On Fri, 01 May 2009 16:15:10 -0700, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
John Larkin wrote:I just got some samples of a Vishay PAD5 picoamp-leakage diode, inWhat are you going to design with that diode then?
SOT23.
Pin 3 to pin 1 ohms as a diode
Pin 3 to pin 2 ohms as a diode
Pin 1 to pin 2 ohms as an 8K resistor.
Next project is to actually measure the forward and reverse curves,
down to pA levels.
It's the amplifier that's going to operate in vacuum. The signal is
nanovolts at very high impedance, with occasional massive RF blasts. I
was thinking of using them as back-to-back clamp diodes to protect the
front end. Vf is 1.5 volts at 10 mA, so they're not going to protect a
lot.
Can't you clamp against two rails and make sure the amp is able to tolerate a few volts? Even if the rails have to be set up just for that purpose. In low current apps simple back-to-back diodes can cause distortion.
Some of the zippy dual-gate low-C FETs such as the BF998 can stomach +/-8V on the gates.
Their zero-bias resistance should be pretty low, but looks like I'll
have to measure it. That's a nisance at pA levels. Maybe I can get one
of those tins full of Danish cookies...
Only if your cholesterol levels are ok :-)
I have a huge copper box for such jobs and for EMI hunting. About 2-3ft long/wide/high. Depending on the weather, when moving its lid you can often see a bright blue flash and hear a pop.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
.
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