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.
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Brooke Clarke
http://www.PRC68.com
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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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