Basic CE Amplifier

384

06:08:06

Look at the currents and voltages. Adjust by turning off the current views or by turning the voltages off to see the affect on each. 

This is a CE (Common-Emitter) Small Signal Amplifier and is one of the most common amplifiers.

Notice the small resistor and the large resistor that is in parallel with the capacitor. This is so that you have a stable Q Point (Beta/Alpha/hFE), high voltage gain, and a stable voltage gain. This is the most optimal connection so that in the DC analysis you have a small resistance, and in the AC analysis you have the large resistance for stability.

There’s many other forms of amplification, this I believe leads to Operational Amplifiers and how they function. Interestingly how transistors have a equivalent circuit with a defendant current source is the same if not very similar to how Op Amps are presented in Linear Circuit Analysis. 

Also notice that the output signal is 180 degrees of phase. This is natural for a CE Amplifier.

published 5 years ago

PrathikP

5 years ago

Have you noticed that the output is quite heavily distorted? It is due to the fact that the transistor is not biased property. Also, you have used 1KF (kilofarad, aka 1000F) capacitors which is a billion times larger than what is typically used (like 1uF) for example. Try again by starting from recalculating the resistor values and the Q point.

xanquilty

5 years ago

I wasn’t sure what capacitor values to use because in the problems we did the Capacitance was “approaching infinity”. And I was wondering myself why that was happening. I’ll go through one of my homework problems and remake the circuit.

xanquilty

5 years ago

I fixed it now. For now I used a Amplifier from my lab, but it is absolutely essential to do analysis before designing a amplifier to make sure the “DC Load Line” and “AC Load Line” both intersect the “Q-Point”. Look up these topics for more info.

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