I didn't get it.Can you explain where exactly is the output current taken from CE amplifier?Hi D,,
You say collector current, how can that flow in the output load resistor.?
E
So what is the point of current amplification(hfe)?hi D,
The Collector Current refers to the actual current flowing into the Transistors Collector path to Emitter and 0V.
The current flowing in the Collector resistor will be the same as the Collector current if there is no output loading.
If the transistor drives an external as shown in your diagram, the Collector does not source the current into the external load, the current in the collector resistor is the sum of the actual Collector current and the external load current.
Do you follow, OK.?
E
What i meant was, if the load draws current in addition to the collector current,then how is the load controlled?hi D,
The hfe refers to Base to Collector current amplification.
E
hi,how is the load controlled?
That explains it.Thank you very much Eric.hi,
It is controlled by the voltage level of the Collector, which in turn is controlled by the Base current and hfe
E
What if we don't use the bypass capacitor?hi,
Consider the effective impedance of the bypass capacitor in parallel with the emitter resistor, at different frequencies
Their combined impedance determines the Negative feedback of the amplifier.
E
Isn't that what we want?Fixed gain
The sentence "When the impedance of RE||C2 decreases....." could be misinterpreted having the given expression (see post#17) for the gain (-RL/RE) in mind.The circuit diagram shown below is your classic common emitter amplifier.
Without C2 the AC gain is -RL/RE independent of frequency.
RE introduces negative feedback. When the impedance of RE//C2 decreases, negative feedback decreases also.
Since the impedance of C2 is a function of frequency, the AC gain becomes a function of AC frequency.