We were tasked to create a 3 stage amplifier to connect a microphone to an 8ohm speaker, with the first stage being a FET, the second a BJT, and the third an op-amp, whose only purpose is to be a voltage follower to drive the speaker, rather then having the BJT driving the speaker. In input from the microphone is 20mV peak-peak, and we want to amplify to about 5V Peak-Peak.
The following is what I have so far. What I don't understand is why the voltage drops through the voltage follower, nor why a negative DC bias exists at prob 3, between the capacitor and the op-amp. Any suggestions/thoughts? Thanks!
http://img146.imageshack.us/img146/3897/amplifiercircuit.jpg
The following is what I have so far. What I don't understand is why the voltage drops through the voltage follower, nor why a negative DC bias exists at prob 3, between the capacitor and the op-amp. Any suggestions/thoughts? Thanks!
http://img146.imageshack.us/img146/3897/amplifiercircuit.jpg