Electronic Devices - BJT and FET Frequency Response - Discussion
Discussion Forum : BJT and FET Frequency Response - General Questions (Q.No. 7)
7.
An amplifier rated at 30-W output is connected to a 5-
speaker. Calculate the input voltage for the rated output if the amplifier voltage gain is 20 dB.
speaker. Calculate the input voltage for the rated output if the amplifier voltage gain is 20 dB.Discussion:
3 comments Page 1 of 1.
Mae said:
6 years ago
Adb=20log(Av).
Where:
Adb=20
let Av=x.
20=20log(x)
*Shift solve
x=Av=10.
Po=(Vo^2/R).
Where:
Po=30 W.
R=5 ohms.
let Vo=x.
30=(x^2/5).
*Shift solve,
x=Vo=12.247.
Av=Vo/Vi.
Where:
Av=10.
Vo=12.247 V.
let Vi=x.
10=12.247/x
*Shift solve,
x=Vi=1.225 V.
Where:
Adb=20
let Av=x.
20=20log(x)
*Shift solve
x=Av=10.
Po=(Vo^2/R).
Where:
Po=30 W.
R=5 ohms.
let Vo=x.
30=(x^2/5).
*Shift solve,
x=Vo=12.247.
Av=Vo/Vi.
Where:
Av=10.
Vo=12.247 V.
let Vi=x.
10=12.247/x
*Shift solve,
x=Vi=1.225 V.
(1)
Junayd said:
1 decade ago
Av = Vo/Vi = 10^(gain in db/20).
===> 10^(20/20) = 10^1 = 10 = Vo/Vi.
===> Vi = Vo/10.1.
***Now for Vo***.
P = Vo^2/R ===> Vo = sqrt(PR) = 12.25.
***Put Vo in equation 1***.
Vi = 12.25/10 = 1.225V.
===> 10^(20/20) = 10^1 = 10 = Vo/Vi.
===> Vi = Vo/10.1.
***Now for Vo***.
P = Vo^2/R ===> Vo = sqrt(PR) = 12.25.
***Put Vo in equation 1***.
Vi = 12.25/10 = 1.225V.
Tle said:
5 years ago
G = 20log(Vo/Vi)
G = 20log ((√ PR)/Vi)
20db = 20log((√ (30)(5))/Vi).
Vi = 1.2247V.
G = 20log ((√ PR)/Vi)
20db = 20log((√ (30)(5))/Vi).
Vi = 1.2247V.
(2)
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