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.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
+−5 VR = ?2.1 V15 mA

A yellow LED with a forward voltage of 2.1 V runs from a 5 V supply through a series resistor. Find the resistance R that sets the LED current to 15 mA.

Vs = 5 VVF = 2.1 VI = 15 mA
R = Ω
2.Easy
+−24 V220 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 24 V through a 220 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 24 VVZ = 6.2 VR = 220 Ω
IR = mA
3.Medium
+−12 V220 Ω9.1 V3300 ΩIZ​ = ?

A 9.1 V Zener regulator is fed from 12 V through 220 Ω and supplies a 3300 Ω load. Find the Zener current IZ.

Vin = 12 VVZ = 9.1 VR = 220 ΩRL = 3300 Ω
IZ = mA
4.Medium
+−20 V270 Ω3.3 V1000 ΩIZ​ = ?

A 3.3 V Zener regulator is fed from 20 V through 270 Ω and supplies a 1000 Ω load. Find the Zener current IZ.

Vin = 20 VVZ = 3.3 VR = 270 ΩRL = 1000 Ω
IZ = mA
5.Hard
RC​ = 150 Ωβ = 150VCC​ = 9 V3.3 VRB​ = ?

An NPN transistor with β = 150 switches a 150 Ω load resistor connected between VCC = 9 V and its collector. The emitter is grounded. The base is driven from a 3.3 V logic output through a base resistor RB. Take VBE = 0.7 V and VCE(sat) = 0.2 V. For reliable switching, design for a base current 10 times the minimum needed for saturation. Find RB in kΩ.

VCC = 9 VRC = 150 Ωβ = 150Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 10
RB = kΩ
6.Hard
V (V)I (mA)0.6627.27Q = ?

A diode is modelled as 0.6 V in series with 5 Ω (it conducts above 0.6 V). It is in series with a 220 Ω resistor across a 6 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 6 VR = 220 ΩV0 = 0.6 Vrd = 5 Ω
ID = mA

Answer key

  1. 1. R = 193.3 Ω
  2. 2. IR = 80.91 mA
  3. 3. IZ = 10.42 mA
  4. 4. IZ = 58.55 mA
  5. 5. RB = 0.6648 kΩ
  6. 6. ID = 24 mA

Full step-by-step solutions: practise this topic on examproblems.com.