What is the difference in applying -ve voltage at emitter and +ve coll

dexterdev

What is the difference in applying -ve voltage at emitter and +ve voltage at collector in attached circuit image? Really what I think is both circuits in thae image are identical. But then why -VEE?

-Devanand T

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vk6kro

The power supply voltages also affect the necessary input voltages.

For example in the second diagram, the transistor with -1.3 volts on its base will be turned off if the negative supply line is grounded but it is conducting if this line is at -5.2 volts.

This is because the base is more positive than the negative supply line in the second case, but less positive in the first case.

NascentOxygen

Over what range of input voltages will the arrangement in (a) function as an amplifier?

What about (b)?

dexterdev

the circuit in (a) is basic ECL unit, range of inputs is 2 logic states at input -1.7 V and -0.8 V.

I was asking that what difference (a) has with (b) in voltage supply applied in terms of polarity.

NascentOxygen

(b) will function in the same manner, but not with the input/output voltages that cause (a) to work.