>How does one calculate the input impedence of a GG amplifier?
>
// The input Z is a 360º average of essentially E-in/I-in During the
negative half of the driving sinewave, I is maximal, so Z is low. During
the positive half of the driving sinewave, Z is high because current is
mostly cut-off. // A rule of thumb is that Z-in-avg is c. 55% of the
instantaneous E/I ratio at the negative peak of the driving sinewave.
My guess is that published Zin figures are found by adjusting the input
Pi network until a good match is obtained, measuring the values of C1,
C2, and L1, and then calculating the Z value.
cheers
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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