reza17,
ednan said:
(iv)Feedback can incease the gain of a system in one frequency range but decrease in another.
Seems like on the face of it, this is True, as Kral said.
Take a "system", an op-amp, with a capacitor in the negative feedback loop. At frequency X it has unity gain...by my definition. In the frequency range [f<X] the gain will increase with a decrease in frequency. In the frequency range [f>X] the gain will decrease with a increase in frequency.
Ken