[sdiy] tube question 2: characteristics , DC versus 20kHz

[Antti Huovilainen]

On Thu, 28 Aug 2003, Czech Martin wrote:

> is it true that e.g. a triode stage large signal
> characteristic measured at DC differs from
> those measured at -say- 10kHz or 20kHz?

It is true for the often used bypassed cathode configuration (which will
give you roughly twice the gain at frequencies higher than the RC cutoff
point). Other than that the tube parasitic capacitances have some effect,
but you can calculate the effect yourself. Typical capacitances are shown
in the datasheets.

Antti

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