# common emitter and common source amplifier

Discussion in 'Homework Help' started by teivel, Oct 13, 2014.

1. ### teivel Thread Starter New Member

Jul 9, 2014
4
0
1. how to onvert the amplifier gains between decibels and (unitless) ratios ?
for example
i) AV = 14.1 dB ; AV(ratio) =
ii) AI = 202 ; AI(dB) =
iii) AP = 15 dB ; AP(ratio) =

2. A BC177 is used in common emitter mode with a 4k7 collector resistor. If hie = 1k, hfe=125, hoe=20x10-6s
determine Rin, Rout, Ai, gm, Av
3. A JFET is used in common source mode with a 8k2 load resistor. If
gm = 30 mS and rds= 40 k ohm

determine Av

4. An amplifier without feedback produces a fundamental component of output voltage of 30 volts with second harmonic component B2 in the output of amplifiers due to non-linearity of 5% distortion content when input voltage VIN is 0.02 volts.
(a) Calculate the open loop gain of the amplifier.
(b) If 1% of the output is fed back to the input as a negative voltage series feedback,
calculate the magnitude of the output voltage.
(c) If the fundamental frequency component of the output voltage is maintained at 30 volts,
but the second harmonic distortion B2.F is reduced to 1%, calculate the input voltage.

2. ### Papabravo Expert

Feb 24, 2006
10,338
1,850
1. Use the definition. If AV = 20* log(Vo/Vi), then 10^(AV/20) = Vo/Vi
It's High School Algebra, to do the same thing to both sides of an equation leaving it unchanged.

teivel likes this.

Jul 9, 2014
4
0
thanks

4. ### WBahn Moderator

Mar 31, 2012
18,069
4,905
Is AP a power ratio?