CE Transistor Amplifier

[regale]

Hi,
I am trying to amplify the ac input signal but any input value results in 0V output, Can anyone what's wrong with my circuit? I don't want to use a voltage divider bias configuration.

 

[LvW]

The first thing I was taught about biasing a transistor is to never simply use one base resistor to a supply voltage.
Because each transistor has a different current gain and has a different base-emitter voltage even if they have the same part number.

Also, the current gain increases as the transistor heats up.
Therefore a voltage divider biases the base plus an emitter resistor is added to 0V.
Sometimes a biasing resistor is connecting between the collector and base for negative feedback.

Comment 1: "Different base-emitter voltage"? A transistor does not "have" such a voltage. The base-emitter voltage Vbe is applied externally - and it has a certain relationship to the emitter resp. collector current as defined by the well known exponential formula (which, however, is remarkably temperature sensitive).

Comment 2: From the last sentence one could get the impression that such a resistor between C and B should/could be used in addition to an emitter resistor. No, this is not recommended - this would be counter productive.
It is the emitter resistor which provides negative feedback and, thus, stabilizes the device against the temperature influence as mentioned in my comment 1 above.

 

[LvW]

There is one disadvantage of the shown bias scheme if compared with the Re method (emitter resistor):
The input resistance is reduced (Miller effect) whereas RE will increase the input resistance.
For this reason, I think that the Re-feedback is the preferred method for stabilizing the Q-point,

 

[crutschow]

There is one disadvantage of the shown bias scheme if compared with the Re method (emitter resistor):
The input resistance is reduced (Miller effect)

Yes, although the input impedance is likely dominated by the low Rbe of a grounded-emitter amp (in the neighborhood of a few kΩ, depending upon the emitter current).

Interesting, the distortion of a grounded emitter amp due to the non-linear input current versus input voltage, can be reduced if the base drive is a high-impedance (constant-current) source, such as from the collector of a common-emitter input stage.