I have a few questions about pp. 90-93 of the "Student Manual for the Art of Electronics" (attached), which describes how to choose the specific component values for an emitter follower circuit. On p. 92, it talks about making the bias "stiff enough." What do they mean by "stiff"? And stiff enough...for what?
Also on p.92, they calculate the impedance looking into the entire circuit. To do this, they use the Thevenin equivalent of the two bias resistors. I don't see how this makes sense, however...shouldn't you just use the lower bias resistor (the one directly connected to ground), since current passing through the capacitor cannot possibly pass through the upper bias resistor (since to do so it would be going to higher potential)? It seems to me that to calculate the impedance of the entire circuit, looking in from the capacitor, you should calculate R_2 parallel (R_E parallel R_load). Why is this wrong?
Thanks in advance for the help.
Also on p.92, they calculate the impedance looking into the entire circuit. To do this, they use the Thevenin equivalent of the two bias resistors. I don't see how this makes sense, however...shouldn't you just use the lower bias resistor (the one directly connected to ground), since current passing through the capacitor cannot possibly pass through the upper bias resistor (since to do so it would be going to higher potential)? It seems to me that to calculate the impedance of the entire circuit, looking in from the capacitor, you should calculate R_2 parallel (R_E parallel R_load). Why is this wrong?
Thanks in advance for the help.
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