The base current is $100 \mu A$ and the collector current is $3 \text{ mA}$. $A$ change of $20 \mu A$ in the base current results in a change of $0.5 \text{ mA}$ in the collector current. The value of $\beta_{ac}$ is:

In a common emitter transistor amplifier, the output resistance is $500 \text{ k}\Omega$ and the current gain $\beta = 50$. If the power gain of the amplifier is $5 \times 10^6$, what is the input resistance (in $\Omega$)?

For a common emitter configuration,if $\alpha$ and $\beta$ have their usual meanings,the incorrect relation between $\alpha$ and $\beta$ is

To use a transistor as an amplifier,

The current gain for a transistor working as a common base amplifier is $0.96$. If the emitter current is $7.2 \,mA$, then the base current is (in $\,mA$)

For transistor action:
$(1)$ Base,emitter and collector regions should have similar size and doping concentrations.
$(2)$ The base region must be very thin and lightly doped.
$(3)$ The emitter-base junction is forward biased and base-collector junction is reverse biased.
$(4)$ Both the emitter-base junction as well as the base-collector junction are forward biased.
Which one of the following pairs of statements is correct?