Paul Burridge wrote in message . ..

What's a doubler based on the good old 1N4148 good for, top end
frequency-wise?

Thanks to Jan-Martin for his reference to some actual experiments.

But in reply to Paul, I'd ask: Do you understand how the "full-wave
rectifier doubler" works, basically? (Ideal waveforms and all that.)
Do you have a data sheet for the 1N4148? What items from the data
sheet do you suppose might limit the useful frequency? Can you make
an estimate, based on the data sheet numbers? What would you do in a
design to extend the frequency range for a given diode characteristic?
For example, what does diode capacitance do to circuit operation?
What does reverse recovery do? In the full-wave frequency doubler
circuit, what does the input impedance look like, assuming an ideal
transformer, when one diode is forward biased and the other is
reverse-recovering? Can you think of parts to add to cause that to
not be so much of a problem (assuming it is a problem)?

Thinking about this sort of thing is useful not only in figuring out
what to expect, at least ball-park, but also in getting better
performance out of someone else's circuit and/or understanding its
limitations.

Cheers,
Tom