$$A$$ transistor has a voltage gain $$A$$. If the amount $$\beta A$$ of its output is applied to the input of the transistor, then the transistor becomes oscillator, when

At absolute zero temperature, pure silicon behaves as

In common emitter amplifier, input resistance is $$1000 \Omega$$, peak value of input signal voltage is $$5 \mathrm{~mV}$$ and $$\beta=60$$. The peak value of output current is

When a small amount of impurity atoms are added to a semiconductor, then generally its resistivity