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 = ?2.2 V25 mA

A green LED with a forward voltage of 2.2 V runs from a 5 V supply through a series resistor. Find the resistance R that sets the LED current to 25 mA.

Vs = 5 VVF = 2.2 VI = 25 mA
R = Ω
2.Easy
+−20 V220 Ω3.3 VIR​ = ?

A 3.3 V Zener diode is fed from 20 V through a 220 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 20 VVZ = 3.3 VR = 220 Ω
IR = mA
3.Medium
RC​ = 5.6 kΩβ = 200RE​ = 2.2 kΩVCC​ = 15 VR1​ = 100 kΩR2​ = 22 kΩ

An NPN transistor with β = 200 has voltage-divider bias from VCC = 15 V: R₁ = 100 kΩ from VCC to the base and R₂ = 22 kΩ from the base to ground. The collector resistor is RC = 5.6 kΩ and the emitter resistor is RE = 2.2 kΩ. Take VBE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector–emitter voltage VCE.

VCC = 15 VR1 = 100 kΩR2 = 22 kΩRC = 5.6 kΩRE = 2.2 kΩβ = 200
VCE = V
4.Medium
RC​ = 1.5 kΩβ = 150VCC​ = 9 VRB​ = 330 kΩ

An NPN transistor with β = 150 is biased by a base resistor RB = 330 kΩ from the supply VCC = 9 V. The collector resistor is RC = 1.5 kΩ and the emitter is grounded. Take VBE = 0.7 V and assume the transistor is in the active region. Find the collector–emitter voltage VCE.

VCC = 9 VRB = 330 kΩRC = 1.5 kΩβ = 150VBE = 0.7 V
VCE = V
5.Hard
RC​ = 150 Ωβ = 50VCC​ = 5 V3.3 VRB​ = ?

An NPN transistor with β = 50 switches a 150 Ω load resistor connected between VCC = 5 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. Find the largest base resistor RB, in kΩ, that still drives the transistor just into saturation.

VCC = 5 VRC = 150 Ωβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ
6.Hard
+−≥ 12 VR = ?3.3 V≤ 25 mA

A 3.3 V Zener regulator must supply up to 25 mA to a load. The input can drop to 12 V, and the Zener needs at least 2 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 12 VVZ = 3.3 VIL,max = 25 mAIZ,min = 2 mA
Rmax = Ω

Answer key

  1. 1. R = 112 Ω
  2. 2. IR = 75.91 mA
  3. 3. VCE = 8.195 V
  4. 4. VCE = 3.341 V
  5. 5. RB = 4.062 kΩ
  6. 6. Rmax = 322.2 Ω

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