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 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
2.Easy
+−12 VR = ?2 V20 mA

A red LED with a forward voltage of 2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 20 mA.

Vs = 12 VVF = 2 VI = 20 mA
R = Ω
3.Medium
+−20 V270 Ω5.1 V1500 ΩIZ​ = ?

A 5.1 V Zener regulator is fed from 20 V through 270 Ω and supplies a 1500 Ω load. Find the Zener current IZ.

Vin = 20 VVZ = 5.1 VR = 270 ΩRL = 1500 Ω
IZ = mA
4.Medium
RC​ = 1.2 kΩβ = 150VCC​ = 9 VRB​ = 220 kΩ

An NPN transistor with β = 150 is biased by a base resistor RB = 220 kΩ from the supply VCC = 9 V. The collector resistor is RC = 1.2 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 = 220 kΩRC = 1.2 kΩβ = 150VBE = 0.7 V
VCE = V
5.Hard
RC​ = 150 Ωβ = 200VCC​ = 24 V5 VRB​ = ?

An NPN transistor with β = 200 switches a 150 Ω load resistor connected between VCC = 24 V and its collector. The emitter is grounded. The base is driven from a 5 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 3 times the minimum needed for saturation. Find RB in kΩ.

VCC = 24 VRC = 150 Ωβ = 200Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 3
RB = kΩ
6.Hard
RC​ = 330 Ωβ = 50IC​ = ?VCC​ = 24 V3.3 VRB​ = 47 kΩ

An NPN transistor with β = 50 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 = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 47 kΩ
IC = mA

Answer key

  1. 1. IR = 15.45 mA
  2. 2. R = 500 Ω
  3. 3. IZ = 51.79 mA
  4. 4. VCE = 2.209 V
  5. 5. RB = 1.807 kΩ
  6. 6. IC = 2.766 mA

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