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--- cert_exam:electrical_chief_engineer_3:theory:electronic_theory:amplifier [2020/08/10 16:53] – [利得] fu
+++ cert_exam:electrical_chief_engineer_3:theory:electronic_theory:amplifier [2020/08/10 16:57] (current) – fu
@@ Line 20: / Line 20: @@
 電力利得
 $ G_p [dB] = 10 log \frac{P_o}{P_i} $
+=== log に関わる公式 ===
+\[
+log (a * b) = log a + log b \\
+log (\frac{a}{b}) = log a - log b \\
+\]
+例\\
+log 5 = log (10/2) = log 10 - log 2 \\
+で計算できる
 ==== 利得を計算する式の数が，電力利得は20，電圧利得は10なのはなぜ? ====