I have a few questions about the circuit above.
1. The job of the differential amplifier is to amplify the difference between the two input signals. Can't I just use two CE Amplifiers and connect the emitters together to one emitter resistor? After all, it will do the same job.
2. On most bjt differential amplifier circuits I see that the emitters are connected not to 0v, but to some negative voltage like -12v. Does that mean I need two batteries in series so that the middle point is 0volts, the top is +12v and the bottom -12v?
3. If we do need to commect the emitters to a negative voltage, then why do we do so, what is the reason behind this?
4. How do I calculate the emitter resistor? I mean, in CE Amplifiers I usualy leave 1volt to RE, is it the same case?