Diodes & transistors worksheet with answers

Free printable Diodes & transistors worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
+−20 V150 Ω5.1 VIR​ = ?

A 5.1 V Zener diode is fed from 20 V through a 150 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 20 VVZ = 5.1 VR = 150 Ω
IR = mA
2.Easy
+−Vs​5 VR = 2.2 kΩD​I = ?

A 5 V DC source drives current through a 2.2 kΩ resistor in series with a forward-biased silicon diode. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 5 VR = 2.2 kΩVD = 0.7 V
I = mA
3.Medium
RC​ = 1.5 kΩβ = 150IC​ = ?RE​ = 1.5 kΩVCC​ = 15 VR1​ = 22 kΩR2​ = 8.2 kΩ

An NPN transistor with β = 150 has voltage-divider bias from VCC = 15 V: R₁ = 22 kΩ from VCC to the base and R₂ = 8.2 kΩ from the base to ground. The collector resistor is RC = 1.5 kΩ and the emitter resistor is RE = 1.5 kΩ. Take VBE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector current IC in mA.

VCC = 15 VR1 = 22 kΩR2 = 8.2 kΩRC = 1.5 kΩRE = 1.5 kΩβ = 150
IC = mA
4.Medium
RC​ = 2.7 kΩβ = 50IC​ = ?VCC​ = 15 VRB​ = 390 kΩ

An NPN transistor with β = 50 is biased by a base resistor RB = 390 kΩ from the supply VCC = 15 V. The collector resistor is RC = 2.7 kΩ and the emitter is grounded. Take VBE = 0.7 V and assume the transistor is in the active region. Find the collector current IC in mA.

VCC = 15 VRB = 390 kΩRC = 2.7 kΩβ = 50VBE = 0.7 V
IC = mA
5.Hard
+−≥ 24 VR = ?5.1 V≤ 50 mA

A 5.1 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 1 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 24 VVZ = 5.1 VIL,max = 50 mAIZ,min = 1 mA
Rmax = Ω
6.Hard
V (V)I (mA)0.651212Q = ?

A diode is modelled as 0.65 V in series with 10 Ω (it conducts above 0.65 V). It is in series with a 1000 Ω resistor across a 12 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 12 VR = 1000 ΩV0 = 0.65 Vrd = 10 Ω
ID = mA

Answer key

  1. 1. IR = 99.33 mA
  2. 2. I = 1.955 mA
  3. 3. IC = 2.176 mA
  4. 4. IC = 1.833 mA
  5. 5. Rmax = 370.6 Ω
  6. 6. ID = 11.24 mA

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