So what's going on? How come a low output impedance is desirable? Surely, something must be wrong with the way I'm analyzing the circuit!

Medwatt - the answer is simple: A low output impedance is desirable - however, a simple circuit like the common emitter stage cannot fulfill your desire. If you want to follow the guideline for a low output resistor (example: Rc= 10 ohms in common emitter circuit) you will have practically no gain. That means: Good output resistance (low) of a circuit that cannot be used. Hence, a trade-off is necessary between two conflicting requirements (gain vs. output resistance).

Note, that such atrade-off is necessary in most of analog electronic circuits. As a consequence, a more complicated circuitry is needed to have high gain with a low output resistance - for example: A two-stage amplifier (common emitter in series with common collector).

(Many years ago, there was a song: "You always can`t get what you want".)

So what's going on? How come a low output impedance is desirable? Surely, something must be wrong with the way I'm analyzing the circuit!

Medwatt - the answer is simple: For a voltage amplifier (voltage output) a low output impedance is desirable - however, a simple circuit like the common emitter stage cannot fulfill your desire. If you want to follow the guideline for a low output resistor (example: Rc= 10 ohms in common emitter circuit) you will have practically no gain. That means: Good output resistance (low) of a circuit that cannot be used. Hence, a trade-off is necessary between two conflicting requirements (gain vs. output resistance).

Note, that such a trade-off is necessary in most of analog electronic circuits. As a consequence, a more complicated circuitry is needed to have high gain with a low output resistance - for example: A two-stage amplifier (common emitter in series with common collector).

(Many years ago, there was a song: "You always can`t get what you want".)