So, I'm trying to design a BJT amplifier to meet some specified requirements. The amplifier should remain in the active region. I want to get a gain of "4", and also have my Voltage output swing to be 6Vpp. The restrictions are that the input impedance must be a minimum of 15kohms, and the output impedance must be no greater than 5kohms. I'm given that I have a supply voltage of 16V, Beta falls in the region of anywhere from 80<->250, and the transistor has a Vbe(active) of 0.7V, Vce(sat) of 0.2V. Vt = 25mV.
For this, I thought about starting off by choosing a CE amplifier with an Reu to meet the requirements (i'm guessing). I'm not exactly sure how to start, but what I did do was try to relate the swing and gain considerations into a single equation.
I did a DC bias from the collector to emitter:
16v = B*Ib*Rc + Vbe(act) + Ib*Rb ; to get an equation for Ib
then I believe that the symmetrical swing should look like:
6Vpp = Ic * Rc (where Ic = Ib * B)
I used the hybrid-pi model for the ac bias.
For the gain:
gain = (vout/vin) and for the common emitter in this scenario, I think that the equation simplifies to:
4 = -(B * Rc) / [(B + 1)*Reu + R(pi)]
doing the ac bias, Rin = R(pi) + (1 + B)Reu
and Rout = Rc
With this, I think I should be able to choose worst case minimums and maximums for Beta and Rout, and solve for what Rin would be. I hope I'm making sense. Please tell me what you think, or if I'm on the right track or not (X_X) thanks!
Also, honestly, I don't really know what to do with RL or Rs or if they matter for this design. How would they affect my calculations?
For this, I thought about starting off by choosing a CE amplifier with an Reu to meet the requirements (i'm guessing). I'm not exactly sure how to start, but what I did do was try to relate the swing and gain considerations into a single equation.
I did a DC bias from the collector to emitter:
16v = B*Ib*Rc + Vbe(act) + Ib*Rb ; to get an equation for Ib
then I believe that the symmetrical swing should look like:
6Vpp = Ic * Rc (where Ic = Ib * B)
I used the hybrid-pi model for the ac bias.
For the gain:
gain = (vout/vin) and for the common emitter in this scenario, I think that the equation simplifies to:
4 = -(B * Rc) / [(B + 1)*Reu + R(pi)]
doing the ac bias, Rin = R(pi) + (1 + B)Reu
and Rout = Rc
With this, I think I should be able to choose worst case minimums and maximums for Beta and Rout, and solve for what Rin would be. I hope I'm making sense. Please tell me what you think, or if I'm on the right track or not (X_X) thanks!
Also, honestly, I don't really know what to do with RL or Rs or if they matter for this design. How would they affect my calculations?
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