The discussion revolves around the behavior of a bipolar transistor amplifier, specifically addressing the output voltage when there is no input signal and the implications of removing a coupling capacitor on gain. Participants explore theoretical expectations, biasing conditions, and methods to maximize gain in the circuit.
Participants express differing views on the expected output voltage without input and the effects of removing the coupling capacitor on gain. There is no consensus on the correct output voltage or the best approach to maximize gain, indicating ongoing debate and exploration of the topic.
Participants reference specific voltage levels and current values based on assumptions about the circuit configuration, which may not be universally applicable. The discussion includes various interpretations of the role of components in the amplifier's performance, highlighting potential dependencies on specific circuit designs.
The gain of that configuration is about -Rc/Re, where Re is the sum of the intrinsic emitter resistance re and the external emitter resistor. You can ground the emitter to maximize the gain, but then your bias point is not as stable over temperature and transistor component variations. Using the capacitor in parallel with the emitter resistor gives you an effective grounding of the emitter at frequencies above 1/2piRC, which gives you max gain there. If you need more gain, you will need to cascade (not cascode...) a couple stages in series, or use a current source instead of the collector resistor.math&science said:One more question, if you have an input but took out the 15microF capacitor, is it possible to increase the gain in any way? I know that if you take out the capacitor, you get a lower gain because that capacitor increases the output voltage.