ericz
Junior Member level 3
Hi everyone,
I have a question about the difference between common emitter amplifier to LC tuned amplifier.
In a common mode amplifier , the gain is the :
= sum of the resistors in the collector/ sum of the resistors in the emitter.
The output voltage in CE is:
Vout= Vcc - Idc*Rc - ic*Rc (where Vcc-Idc*Rc is the DC voltage and ic*Rc is the AC signal).
The voltage in the common emitter output as I understood, will never succeed Vcc.
on the contrary, for LC tuned amplifier, where the collector Load is L||C||Rc (paralell resonance) the voltage can succeed Vcc.
my question is, how come? how can a signal in a LC tuned amplifier can be bigger then Vcc, and if so, why in common emitter it cant?
for example, suppose the collector voltage in common emitter amplifier is 3.2V (for 3.3V p.s) and the gain is 100.
if the Vin is 10mV sin then the AC signal needs to be 1V at the output of the CE amplifier and the voltage at the output should be : 3.2V + 1V*sin(wt) which is 4.2V max and 2.2V min.
In LC tuned amplifier (read the attachement) the voltage can succeed the Vcc.
I will apprichiate your help.
Best regards
I have a question about the difference between common emitter amplifier to LC tuned amplifier.
In a common mode amplifier , the gain is the :
= sum of the resistors in the collector/ sum of the resistors in the emitter.
The output voltage in CE is:
Vout= Vcc - Idc*Rc - ic*Rc (where Vcc-Idc*Rc is the DC voltage and ic*Rc is the AC signal).
The voltage in the common emitter output as I understood, will never succeed Vcc.
on the contrary, for LC tuned amplifier, where the collector Load is L||C||Rc (paralell resonance) the voltage can succeed Vcc.
my question is, how come? how can a signal in a LC tuned amplifier can be bigger then Vcc, and if so, why in common emitter it cant?
for example, suppose the collector voltage in common emitter amplifier is 3.2V (for 3.3V p.s) and the gain is 100.
if the Vin is 10mV sin then the AC signal needs to be 1V at the output of the CE amplifier and the voltage at the output should be : 3.2V + 1V*sin(wt) which is 4.2V max and 2.2V min.
In LC tuned amplifier (read the attachement) the voltage can succeed the Vcc.
I will apprichiate your help.
Best regards