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 _________.

For the DC analysis of the Common-Emitter amplifier shown, neglect the base current and assume that the emitter and collector current are equal. Given that V_T = 25mV, V_BE = 0.7V, and the BJT output r₀ is practically infinite. Under these conditions the midband voltage gain magnitude, a_v = $$\left| {{v_0}/{v_i}} \right|\,\,\,V/V,$$ is _____

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 _______.