Diodes & transistors worksheet with answers

A 6 V DC source drives current through a 4.7 kΩ resistor in series with two forward-biased silicon diodes. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

A 6 V DC source is connected through resistor R₁ = 330 Ω to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 1.5 kΩ, and a silicon diode with its anode at X. Use the constant-drop model with 0.7 V. Find the diode current I_D in mA.

An NPN transistor with β = 75 is biased by a base resistor R_B = 470 kΩ from the supply V_CC = 15 V. The collector resistor is R_C = 3.3 kΩ and the emitter is grounded. Take V_BE = 0.7 V and assume the transistor is in the active region. Find the collector current I_C in mA.

An NPN transistor with β = 150 has voltage-divider bias from V_CC = 18 V: R₁ = 82 kΩ from V_CC to the base and R₂ = 12 kΩ from the base to ground. The collector resistor is R_C = 4.7 kΩ and the emitter resistor is R_E = 1 kΩ. Take V_BE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector current I_C in mA.

A 3.3 V Zener regulator must supply up to 50 mA to a load. The input can drop to 24 V, and the Zener needs at least 2 mA to regulate. Find the largest series resistance R_max that keeps it regulating.

A diode is modelled as 0.65 V in series with 20 Ω (it conducts above 0.65 V). It is in series with a 470 Ω resistor across a 6 V supply. Find the operating current I_D where the diode line meets the load line.