In an oscillator,for sustained oscillations,the Barkhausen criterion is $A \beta$ equal to (where $A =$ voltage gain without feedback,$\beta =$ feedback factor).

$A$ thermoelectric refrigerator works on

Given below are two statements:
Statement $I$: Photovoltaic devices can convert optical radiation into electricity.
Statement $II$: Zener diode is designed to operate under reverse bias in the breakdown region.
In the light of the above statements,choose the most appropriate answer from the options given below:

An amplifier has a voltage gain $A_v = 1000$. The voltage gain in $dB$ is...........

Which of the following $p-n$ junction devices is not used in reverse bias?

The correct curve between voltage gain $({A_v})$ and load resistance $({R_L})$ is