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
+−24 V680 Ω5.1 VIR​ = ?

A 5.1 V Zener diode is fed from 24 V through a 680 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 24 VVZ = 5.1 VR = 680 Ω
IR = mA
2.Easy
+−9 V220 Ω5.6 VIR​ = ?

A 5.6 V Zener diode is fed from 9 V through a 220 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 9 VVZ = 5.6 VR = 220 Ω
IR = mA
3.Medium
RC​ = 3.3 kΩβ = 200IC​ = ?RE​ = 680 ΩVCC​ = 15 VR1​ = 100 kΩR2​ = 12 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 = 12 kΩ from the base to ground. The collector resistor is RC = 3.3 kΩ and the emitter resistor is RE = 680 Ω. 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 = 100 kΩR2 = 12 kΩRC = 3.3 kΩRE = 680 Ωβ = 200
IC = mA
4.Medium
+−12 VR = ?3 × 3.2 V5 mA

3 blue LEDs (forward voltage 3.2 V each) are connected in series with a resistor to a 12 V supply. Find the resistance R that sets the current to 5 mA.

Vs = 12 VVF = 3.2 Vn = 3I = 5 mA
R = Ω
5.Hard
+−≥ 20 VR = ?6.2 V≤ 50 mA

A 6.2 V Zener regulator must supply up to 50 mA to a load. The input can drop to 20 V, and the Zener needs at least 5 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 20 VVZ = 6.2 VIL,max = 50 mAIZ,min = 5 mA
Rmax = Ω
6.Hard
RC​ = 680 Ωβ = 100IC​ = ?VCC​ = 9 V3.3 VRB​ = 100 kΩ

An NPN transistor with β = 100 switches a 680 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 = 100 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 = 9 VRC = 680 Ωβ = 100Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 100 kΩ
IC = mA

Answer key

  1. 1. IR = 27.79 mA
  2. 2. IR = 15.45 mA
  3. 3. IC = 1.231 mA
  4. 4. R = 480 Ω
  5. 5. Rmax = 250.9 Ω
  6. 6. IC = 2.6 mA

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