Two Stage Amplifier Lab - Help

[otpowell]

Everyone, I need a little help.  I am doing a lab on two stage amplifiers using 2N3904 transistors.    If you look at the attached pic, there's a V_IN indicated on the negative pole of the capacitor.  When building the circuit, where does the V_IN connect to?  Or is is open?  I connected it to ground.  In the next circuit we have a sine wave coming in through this Vin, but in this stage of it I am supposed to take measurements without the Vin connected to the a sine wave signal.  Any clarification or suggestions would be much appreciated.  Thanks!

[T3sl4co1l]

In the absence of an input signal, a short circuit, matched impedance termination, or open circuit may be appropriate.  Depends on what you're analyzing.

For "this stage of it", you should be able to determine, analytically, whether it makes a difference.

Tim

[otpowell]

Thanks Tim, It's open.   

[dom0]

I'd take a guess and say this exercise is supposed to introduce you to the DC working point of this amplifier.

[otpowell]

I'd take a guess and say this exercise is supposed to introduce you to the DC working point of this amplifier.

The DC voltage stays static.  It's the resistance on the emitter that changes which feeds into the collector of the 2nd transistor.  This is a 2 stage CE CC feedback amplifier, I think.  I'm not really sure what changing the resistance does lol, but the gain seems to be biggest when the resistance is at maximum around 5k ohm.  I'm getting about 1.5 volts RMS @ output when gain is at maximum.  Which doesn't seem like much gain since we have 12v dc going in.  I'm pretty sure I have it hooked up properly.. I guess it's the 100mV pp AC signal that's getting amplified, not the DC voltage.   My gain is calculated to be 48, is that 48 times the input voltage?  So if I convert the 1.5 to P to P, that's 4.29volts.  100mv *48 is 4.8 volts so that's approximately correct?