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
+−9 VR = ?3.2 V20 mA

A blue LED with a forward voltage of 3.2 V runs from a 9 V supply through a series resistor. Find the resistance R that sets the LED current to 20 mA.

Vs = 9 VVF = 3.2 VI = 20 mA
R = Ω
2.Easy
+−20 V220 Ω5.1 VIR​ = ?

A 5.1 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 = 5.1 VR = 220 Ω
IR = mA
3.Medium
RC​ = 2.7 kΩβ = 75IC​ = ?VCC​ = 12 VRB​ = 820 kΩ

An NPN transistor with β = 75 is biased by a base resistor RB = 820 kΩ from the supply VCC = 12 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 = 12 VRB = 820 kΩRC = 2.7 kΩβ = 75VBE = 0.7 V
IC = mA
4.Medium
RC​ = 2.7 kΩβ = 100IC​ = ?VCC​ = 15 VRB​ = 330 kΩ

An NPN transistor with β = 100 is biased by a base resistor RB = 330 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 = 330 kΩRC = 2.7 kΩβ = 100VBE = 0.7 V
IC = mA
5.Hard
RC​ = 330 Ωβ = 100IC​ = ?VCC​ = 24 V3.3 VRB​ = 47 kΩ

An NPN transistor with β = 100 switches a 330 Ω load resistor connected between VCC = 24 V and its collector. The emitter is grounded. The base is driven from a 3.3 V logic output through a base resistor RB = 47 kΩ. Take VBE = 0.7 V and VCE(sat) = 0.2 V. Find the collector current IC in mA when the input is high. Decide first whether the transistor is saturated.

VCC = 24 VRC = 330 Ωβ = 100Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 47 kΩ
IC = mA
6.Hard
+−≥ 9 VR = ?6.2 V≤ 30 mA

A 6.2 V Zener regulator must supply up to 30 mA to a load. The input can drop to 9 V, and the Zener needs at least 2 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 9 VVZ = 6.2 VIL,max = 30 mAIZ,min = 2 mA
Rmax = Ω

Answer key

  1. 1. R = 290 Ω
  2. 2. IR = 67.73 mA
  3. 3. IC = 1.034 mA
  4. 4. IC = 4.333 mA
  5. 5. IC = 5.532 mA
  6. 6. Rmax = 87.5 Ω

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