 #1
Hi,
i have a problem with the voltagegain of a commonemitteramplifier.
I have calculated the theoretical value of the gain given by ##G=\frac{\partial U_{a}}{\partial U_{e} } = h_{FE} \frac{R_{c} }{R_{v} }## , which is between 13925 and 7311 for ##420\leq h_{FE} \leq 800## (given by the datasheet of the transistor )
(other important values =## U_{B}=+9V; R_{C}=4,7 kOhm; R_{V}=270 Ohm; U_{e}=0,6V*\sin(2\pi *1kHz*t)##
I have plotted ##U_{e}##and ##U_{a}##with an oscilloscope, and got ##U_{a} = +9V ## for ##U_{e}## smaller than the minimal BaseEmitterVoltage which is 0,5V .
If ##U_{e} \geq 0.5V##, ##U_{a}## sinks to 6,5V.
I understand the qualitative process of ##U_{a}##, but not the quantitative (##U_{a}##should be much smaller, like 6000V, for ##U_{e} \geq 0.5V## ).
So why is the absolute of ##U_{e} ## so small, when it theoreticly should be much bigger.
(Btw sorry for using U instead of V for Voltage, but i already asked this question on a german physicsform and didn't want to redo the formulas.)
Thank you for your help ^^
Edit: Formulas didnt show properly, Used Transistor: BC548C
i have a problem with the voltagegain of a commonemitteramplifier.
I have calculated the theoretical value of the gain given by ##G=\frac{\partial U_{a}}{\partial U_{e} } = h_{FE} \frac{R_{c} }{R_{v} }## , which is between 13925 and 7311 for ##420\leq h_{FE} \leq 800## (given by the datasheet of the transistor )
(other important values =## U_{B}=+9V; R_{C}=4,7 kOhm; R_{V}=270 Ohm; U_{e}=0,6V*\sin(2\pi *1kHz*t)##
I have plotted ##U_{e}##and ##U_{a}##with an oscilloscope, and got ##U_{a} = +9V ## for ##U_{e}## smaller than the minimal BaseEmitterVoltage which is 0,5V .
If ##U_{e} \geq 0.5V##, ##U_{a}## sinks to 6,5V.
I understand the qualitative process of ##U_{a}##, but not the quantitative (##U_{a}##should be much smaller, like 6000V, for ##U_{e} \geq 0.5V## ).
So why is the absolute of ##U_{e} ## so small, when it theoreticly should be much bigger.
(Btw sorry for using U instead of V for Voltage, but i already asked this question on a german physicsform and didn't want to redo the formulas.)
Thank you for your help ^^
Edit: Formulas didnt show properly, Used Transistor: BC548C
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