[time-nuts] 10811

[Alan Melia]

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" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
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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