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 VR = ?3.2 V15 mA

A blue LED with a forward voltage of 3.2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 15 mA.

Vs = 12 VVF = 3.2 VI = 15 mA
R = Ω
2.Easy
+−24 V680 Ω6.2 VIR​ = ?

A 6.2 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 = 6.2 VR = 680 Ω
IR = mA
3.Medium
+−18 V150 Ω6.2 V470 ΩIZ​ = ?

A 6.2 V Zener regulator is fed from 18 V through 150 Ω and supplies a 470 Ω load. Find the Zener current IZ.

Vin = 18 VVZ = 6.2 VR = 150 ΩRL = 470 Ω
IZ = mA
4.Medium
+−9 V220 Ω6.2 V2200 ΩIZ​ = ?

A 6.2 V Zener regulator is fed from 9 V through 220 Ω and supplies a 2200 Ω load. Find the Zener current IZ.

Vin = 9 VVZ = 6.2 VR = 220 ΩRL = 2200 Ω
IZ = mA
5.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. Find the largest base resistor RB, in kΩ, that still drives the transistor just into saturation.

VCC = 12 VRC = 1 kΩβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ
6.Hard
+−≤ 17 V270 Ω6.2 V

A 6.2 V Zener regulator has a 270 Ω series resistor. The input can rise to 17 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 17 VVZ = 6.2 VR = 270 Ω
PZ,max = mW

Answer key

  1. 1. R = 586.7 Ω
  2. 2. IR = 26.18 mA
  3. 3. IZ = 65.48 mA
  4. 4. IZ = 9.909 mA
  5. 5. RB = 11.02 kΩ
  6. 6. PZ,max = 248 mW

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