[time-nuts] Unified VCXO Carrier Board
dk4xp at arcor.de
Sun Oct 25 19:43:57 EDT 2015
Am 23.10.2015 um 21:27 schrieb Charles Steinmetz:
> Use medium-speed transistors, bias both bases from the same low-noise
> voltage reference such as an LM329, capacitively couple the emitters,
> and use a higher supply voltage, for starters. I use
This evening, I have measured some oh so noisy zeners and was pleasantly
Other than one 40+ year old glass diode all of them were pretty low noise.
Since the LM329 was mentioned above, I tried it also. Another surprise.
HOW CAN THEY MAKE SUCH A NOISY SUBSURFACE ZENER???
Bias for the DUTs was a 1K wire resistor from 10 NiMH cells. The bias
source does not
add any visible noise. The "shorted" trace shows the noise floor of the
system. That is
about 220 pV/sqrt Hz. FFT analyzer is an Agilent 89441A. It has strong
1/f noise that is
barely hidden by the preamp. 0 dB = 1nV/sqrt Hz
> MPSH81/MMBTH81s and a power supply of around 20v (see attached
> schematic) for a reasonably
> optimized implementation. Other transistors can be used, but I've
> found that the H81s work better for squaring 1-10MHz sine waves than
> anything else I've tried -- they hit the sweet spot of the
> bandwidth/gain tradeoff and have a nice flat gain vs. current
Are there differences between Fairchild and Motorola?
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