Re: PAD5
- From: Jamie <jamie_ka1lpa_not_valid_after_ka1lpa_@xxxxxxxxxxx>
- Date: Sat, 02 May 2009 20:38:25 -0400
John Larkin wrote:
On Sat, 02 May 2009 11:11:28 -0700, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
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, in
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.
What are you going to design with that diode then?
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.
I'm trying to find suitable diodes; I need to keep total input node
leakage below, say, 10 pA, and capacitance ballpark 10 pF.
There are several issues: input current, input current noise, input
damage from overloads, and transmit/receive recovery time. They all
fight one another, as any good design problem does.
Skyworks makes some spiffy little RF limiter diodes, 0.8 pF, but of
course they don't specify leakage. The RF people usually don't
acknowledge that DC parameters even exist.
isn't because they normally use PIN diodes which of course don't work
at DC as they do at R.F. ?
I'm about halfway through building my diode tester box. I made it
through all the box machining without bleeding even once.
John
--
"I'd rather have a bottle in front of me than a frontal lobotomy"
"Daily Thought:
SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5";
.
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