The forward voltage (V_F) of the LED (D1) is 1.3 V. When the transistor is saturated, the collector-to-emitter voltage (V_CE) is 0.2 V. The ? of the transistor is 100. Assume that V_BE = 0.7V.

a. Find the voltage V₁ when the transistor is saturated. Assume the diode is conducting current. (Hint: KVL.)

b. Find the value of R₁ so that Ic = 20 mA flows when the transistor is saturated.

c. What is the minimum value of I_B that makes the collector current (Ic) equal to 20 mA? (Hint: Use ?)

d. Find R₂ so that I_B = 1 mA. (Hint: KVL and Ohm.)

 

Transistor circuit design: +5V R1 V1 D1 VF Ic IB + +5V V CE + I