Electronics I Lab (BJT Amplifier) Question

Thread Starter


Joined Jun 7, 2007
hello all, i was searching through google, found this site and got lost on it for atleast 45 minutes before i remembered what i was supposed to be doing. lol. good site you all have here, congrats.

anyway, im currently trying to write up a lab report on a BJT Amplifier. i just have one simple question. what is the point of the bjt amp? in our lab we increased the voltage in and the voltage at the collector node decreased whereas the current at the collector node increaded. this was true for 3 seperate resistances in our circuit design.

i just dont know how to exactly explain why the bjt amp is causing that.

thank you in advance. i have a feeling i might be frequenting this site in the future. :)


Joined Feb 24, 2006
The point of any amplifier is to take a small signal (voltage and current) and make a larger copy (voltage and current) to drive a speaker or some other load.

As you have already noticed larger base currents produce larger collector currents, and large collector currents produce small collector voltages. All this means is that the output voltage is not in phase with the input voltage.