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 VR = ?2 V5 mA

A red LED with a forward voltage of 2 V runs from a 24 V supply through a series resistor. Find the resistance R that sets the LED current to 5 mA.

Vs = 24 VVF = 2 VI = 5 mA
R = Ω
2.Easy
+−12 V680 Ω5.1 VIR​ = ?

A 5.1 V Zener diode is fed from 12 V through a 680 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 12 VVZ = 5.1 VR = 680 Ω
IR = mA
3.Medium
RC​ = 2.2 kΩβ = 150VCC​ = 9 VRB​ = 820 kΩ

An NPN transistor with β = 150 is biased by a base resistor RB = 820 kΩ from the supply VCC = 9 V. The collector resistor is RC = 2.2 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 = 820 kΩRC = 2.2 kΩβ = 150VBE = 0.7 V
VCE = V
4.Medium
RC​ = 1 kΩβ = 80RE​ = 680 ΩVCC​ = 18 VR1​ = 56 kΩR2​ = 8.2 kΩ

An NPN transistor with β = 80 has voltage-divider bias from VCC = 18 V: R₁ = 56 kΩ from VCC to the base and R₂ = 8.2 kΩ from the base to ground. The collector resistor is RC = 1 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–emitter voltage VCE.

VCC = 18 VR1 = 56 kΩR2 = 8.2 kΩRC = 1 kΩRE = 680 Ωβ = 80
VCE = V
5.Hard
+−≤ 21 V680 Ω9.1 V

A 9.1 V Zener regulator has a 680 Ω series resistor. The input can rise to 21 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 21 VVZ = 9.1 VR = 680 Ω
PZ,max = mW
6.Hard
+−≤ 19 V330 Ω5.1 V

A 5.1 V Zener regulator has a 330 Ω series resistor. The input can rise to 19 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 19 VVZ = 5.1 VR = 330 Ω
PZ,max = mW

Answer key

  1. 1. R = 4400 Ω
  2. 2. IR = 10.15 mA
  3. 3. VCE = 5.66 V
  4. 4. VCE = 14.53 V
  5. 5. PZ,max = 159.2 mW
  6. 6. PZ,max = 214.8 mW

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