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
+−12 V470 Ω5.6 VIR​ = ?

A 5.6 V Zener diode is fed from 12 V through a 470 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 12 VVZ = 5.6 VR = 470 Ω
IR = mA
2.Easy
+−9 VR = ?3 V20 mA

A white LED with a forward voltage of 3 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 VI = 20 mA
R = Ω
3.Medium
+−20 V270 Ω12 V1000 ΩIZ​ = ?

A 12 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 = 12 VR = 270 ΩRL = 1000 Ω
IZ = mA
4.Medium
+−24 VR = ?4 × 3.2 V20 mA

4 blue LEDs (forward voltage 3.2 V each) are connected in series with a resistor to a 24 V supply. Find the resistance R that sets the current to 20 mA.

Vs = 24 VVF = 3.2 Vn = 4I = 20 mA
R = Ω
5.Hard
RC​ = 220 Ωβ = 80IC​ = ?VCC​ = 12 V5 VRB​ = 3.3 kΩ

An NPN transistor with β = 80 switches a 220 Ω load resistor connected between VCC = 12 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB = 3.3 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 = 12 VRC = 220 Ωβ = 80Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 3.3 kΩ
IC = mA
6.Hard
RC​ = 1 kΩβ = 200IC​ = ?VCC​ = 12 V5 VRB​ = 220 kΩ

An NPN transistor with β = 200 switches a 1 kΩ load resistor connected between VCC = 12 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB = 220 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 = 12 VRC = 1 kΩβ = 200Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 220 kΩ
IC = mA

Answer key

  1. 1. IR = 13.62 mA
  2. 2. R = 300 Ω
  3. 3. IZ = 17.63 mA
  4. 4. R = 560 Ω
  5. 5. IC = 53.64 mA
  6. 6. IC = 3.909 mA

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