Re: PAD5
- From: Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx>
- Date: Sun, 03 May 2009 10:14:53 -0700
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, JoergCan'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.
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:
John Larkin wrote:It's the amplifier that's going to operate in vacuum. The signal isI 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.
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.
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.
You'd have to measure that but I guess it will be disappointing.
I'm about halfway through building my diode tester box. I made it
through all the box machining without bleeding even once.
I'd rather do that as well but the honey-do list said that I had to perform my most favorite task. The yearly pellet stove cleaning. Yuck. Well, at least it won't happen again until spring 2010.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
.
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