24-02-2017, 02:40 PM
Just another point. It is hopefully "stating the obvious", as it applies equally to valve circuits, but just in case...
DC conditions first. Then add signal.
In other words, you must always bias your valve or transistor before it can amplifier the way you want. The AC signal basically "wobbles" the circuit either side of the quiescent DC condition.
The signal at the base-emitter junction of a transistor consists of a DC offset and and AC signal. Learning to mentally separate these two components so you can consider each separately is probably the biggest favour you can do for yourself.
That DC offset is likely to be close to 0.2V for a germanium transistor (0.6V for silicon). Give or take...
If there is an emitter resistance, it'll have a DC offset on it. More on that later if needed.
DC conditions first. Then add signal.
In other words, you must always bias your valve or transistor before it can amplifier the way you want. The AC signal basically "wobbles" the circuit either side of the quiescent DC condition.
The signal at the base-emitter junction of a transistor consists of a DC offset and and AC signal. Learning to mentally separate these two components so you can consider each separately is probably the biggest favour you can do for yourself.
That DC offset is likely to be close to 0.2V for a germanium transistor (0.6V for silicon). Give or take...
If there is an emitter resistance, it'll have a DC offset on it. More on that later if needed.
