In the figure shown, the npn transistor acts as a switch.

For the input v_in(t)as shown in the figure, the transistor switches between the cut-off and saturation regions of operation, when T is large. Assume collector-to-emitter voltage saturation V_CE(sat) = 0.2V and base-to-emitter voltage V_BE = 0.7V. The minimum value of the common-base current gain$$\left( \alpha \right)$$ of the transistor for the switching should be _________.

In the ac equivalent circuit shown, the two BJTs are biased in active region and have identical parameters with β >> 1. The open circuit small signal voltage gain is approximately _______.

In the circuit shown, I₁ = 80 mA and I₂ b= 4mA. Transistors T₁ and T₂ are identical. Assume that the thermal voltage V_T is 26 mV at 27^oC. At 50^oC, the value of the voltage V₁₂ = V₁ - V₂ (in mV) is _______.

Consider the common-collector amplifier in the figure (bias circuitry ensures that the transistor operates in forward active region, but has been omitted for simplicity). Let I_C be the collector current, V_BE be the base-emitter voltage and V_T be the thermal voltage. Also, 𝑔_m and 𝑟_o are the small-signal transconductance and output resistance of the transistor, respectively. Which one of the following conditions ensures a nearly constant small signal voltage gain for a wide range of values of R_E?