common emitter bias question

[Ethan]

how do you determine Rc?  I've read the old thread on BJT biasing but still haven't figured this out.  I know Rc determines the output impedance.  But what do you set this at? 

[R.G.]

Was it my monologue on biasing? It's buried in there.

The collector resistor is set based on the voltage split you decide on for Rc versus Vce versus Re. 

1. decide what voltages you need on the collector and emitter. If it's a CE gain stage, you probably want Vrc and Vce to be about equal, and together about ten times Ve.
2. decide what current you want to flow through the collector emitter path. This needs to be more than you'll ever need to flow out to the load. For high resistance loads, pick a current.
3. When that is done, Rc and Re are defined by Ohm's law.
4. to make these decisions work, design a base voltage supply that puts the base at least one Vbe (0.5 to 0.6V) above the emitter.

The Rc is affected by loading and output impedance, but only tangentially.