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1 某放大器電壓增益在1500Hz為10，在5000Hz為50，若以1500Hz為參考單位，則在5000Hz之分貝增益為?
A 5
B 10 log 5
C 10 log 25
D 20 log 25
  

`A_V(dB)` = `20 log A_V`

= `20 log (50/10)`

= `20 log 5`

= `10*2 log 5`

= `10 log (5^2)`

= `10 log 25`