[time-nuts] Low noise quartz crystal oscillator by Bruce Griffiths

Richard (Rick) Karlquist richard at karlquist.com
Wed Oct 28 17:53:35 EDT 2015

On 10/28/2015 10:38 AM, Hal Murray wrote:
> richard at karlquist.com said:
>> The 2N5179 in the 10811 is selected for minimum beta and Ft at 20 mA, which
>> is the start up condition due to the ALC being at full gain.  It has a
>> special HP part number, so you wouldn't know this just looking at the parts
>> list.
> How much of a difference does that selection step make?
> I'd expect the parts within a batch to be very similar, more so for mature
> parts.

All I can tell you is that Burgoon found a non-zero number of
2N5179's that wouldn't start. Knowing the way things were done,
he probably got a response from the vendor to the effect that
it was simply an unspecified parameter and they only guarantee
JEDEC specs and the transistor(s) he found were not a fluke.
HP greatly discouraged the batch qualification paradigm, although
the did resort to it when justified.  It was not justified for
the 10811.


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