Yes below about 4v is the only place where you get the real "Zener" effect,
as you go above 5v it becomes Avalanche Breakdown. The trick is zener effect
has a negative tempco and avalanche a positive one (I think....they are
opposite senses anyway :-)) ) the result is a regulator diode
("zener"....so called) specced at around 5 to 5.5 volts has a near zero
overall tempco.
Alan
G3NYK
----- Original Message -----
From: "Brooke Clarke" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Tuesday, November 18, 2014 10:31 PM
Subject: Re: [time-nuts] 10811
Hi Rick:
When working on Tunnel Diode amplifiers we used (AFAICR) 5.1 V Zener
diodes to stabilize the lower voltage that drive the diode.
5.1V was supposed to have excellent temperature characteristics in terms
of repeatability (don't remember if low noise was part of the selection
criteria).
http://www.prc68.com/I/Aertech.shtml#TDA
The boards with the terminals have the Zener and a custom compensation
network using both Veco (spelling?) (-TC) and Balco (+TC) and fixed
resistors so that the gain stays constant over mil temperature ranges.
Mail_Attachment --
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Richard (Rick) Karlquist wrote:
On 11/17/2014 5:54 PM, Bert Kehren via time-nuts wrote:
I ground one side of the tuning diode and use the 2 to 12 V as the
external
OCXO for my FRK's along with increasing the time constant. I have not
verified it but I think removing the zener Voltage should also improve
ADEV.
Bert Kehren
The choice for the Zener diode came from my old boss at HP,
who was very knowledgeable about using discrete zener diodes
as low noise references. According to him, this particular
part number has very respectable noise. This is just something
you have to know experientially, there is no theory of zener
noise AFAIK. You might try measuring the noise of the 6.2V
reference voltage directly at baseband, and then multiplying
by the 1 Hz/volt sensitivity. Let us know your results.
Rick Karlquist N6RK
(Now retired from HP/Agilent/Keysight)
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