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 V100 Ω5.6 VIR​ = ?

A 5.6 V Zener diode is fed from 9 V through a 100 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 9 VVZ = 5.6 VR = 100 Ω
IR = mA
2.Easy
+−24 VR = ?2.1 V20 mA

A yellow LED with a forward voltage of 2.1 V runs from a 24 V supply through a series resistor. Find the resistance R that sets the LED current to 20 mA.

Vs = 24 VVF = 2.1 VI = 20 mA
R = Ω
3.Medium
RC​ = 4.7 kΩβ = 80IC​ = ?VCC​ = 9 VRB​ = 820 kΩ

An NPN transistor with β = 80 is biased by a base resistor RB = 820 kΩ from the supply VCC = 9 V. The collector resistor is RC = 4.7 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 = 9 VRB = 820 kΩRC = 4.7 kΩβ = 80VBE = 0.7 V
IC = mA
4.Medium
+−15 V270 Ω5.1 V3300 ΩIZ​ = ?

A 5.1 V Zener regulator is fed from 15 V through 270 Ω and supplies a 3300 Ω load. Find the Zener current IZ.

Vin = 15 VVZ = 5.1 VR = 270 ΩRL = 3300 Ω
IZ = mA
5.Hard
+−≤ 26 V470 Ω3.3 V

A 3.3 V Zener regulator has a 470 Ω series resistor. The input can rise to 26 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 26 VVZ = 3.3 VR = 470 Ω
PZ,max = mW
6.Hard
RC​ = 1 kΩβ = 50VCC​ = 12 V3.3 VRB​ = ?

An NPN transistor with β = 50 switches a 1 kΩ load resistor connected between VCC = 12 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. For reliable switching, design for a base current 2 times the minimum needed for saturation. Find RB in kΩ.

VCC = 12 VRC = 1 kΩβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 2
RB = kΩ

Answer key

  1. 1. IR = 34 mA
  2. 2. R = 1095 Ω
  3. 3. IC = 0.8098 mA
  4. 4. IZ = 35.12 mA
  5. 5. PZ,max = 159.4 mW
  6. 6. RB = 5.508 kΩ

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