Since the output stage is a common emitter stage with series resistive
feedback in the emitter, it will produce higher distortion with high
impedance loads due the increased collector voltage swing and subsequent
larger non linear collector base capacitance modulation combined with
the higher collector impedance.
High impedance loads should also produce smaller output stage input
impedance variation (and consequently greater lower pull) due to the
Early effect and the corresponding smaller absolute variation in the
collector impedance for a given percentage change in load impedance
(provided of course that the corresponding greater collector base swing
doesnt substantially increase the effective value of Early coefficient).
However the difficulty of achieving a high impedance (greater than 1 K
or so) load with high stability at 10MHz shouldn't be underestimated.
Bruce
William H. Fite wrote:
I have it driving a 75 ohm load and have noticed no problems. But then, I'm
not the most obsessive of the nuts... [?]
On Tue, Dec 7, 2010 at 12:32 PM, WarrenS<[email protected]> wrote:
The HP10811's frequency being as sensitive to load as it is.
For the best short and long term frequency stability and Allan noise
performance (and spectrum purity), does the 10811 osc work best if driving a
high impedance or a 50 ohm load ... or other?
ws
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