28-06-2017, 06:07 PM
That would be really instructive! Yes, changing the Ge for Si should require a bit of bias adjustment, but like Mark says, it probably won't matter.
The notes from a few pages ago, recommended 'wasting' about a volt across the emitter resistor, and then if you add the base-emitter voltage (0.3V? Although I'd probably allow 0.2V) you need 1.3V on the base. If you swap the germanium device for a silicon type, without changing anything, it'll gobble up 0.6V of this 1.3V before anything happens, thus you'll only have 0.7V across the emitter resistor. So the silicon device will pass 30% less current, but that may still be enough to do its job.
You could return the current to the original design by reducing the emitter resistor, or altering the base resistors, and seeing if it makes any difference. In an amplifier stage which is coupled to the next, by capacitors or transformers, you won't upset anything by doing this, and it can be fun and instructive.
The notes from a few pages ago, recommended 'wasting' about a volt across the emitter resistor, and then if you add the base-emitter voltage (0.3V? Although I'd probably allow 0.2V) you need 1.3V on the base. If you swap the germanium device for a silicon type, without changing anything, it'll gobble up 0.6V of this 1.3V before anything happens, thus you'll only have 0.7V across the emitter resistor. So the silicon device will pass 30% less current, but that may still be enough to do its job.
You could return the current to the original design by reducing the emitter resistor, or altering the base resistors, and seeing if it makes any difference. In an amplifier stage which is coupled to the next, by capacitors or transformers, you won't upset anything by doing this, and it can be fun and instructive.
