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 = ?2.2 V20 mA

A green LED with a forward voltage of 2.2 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 = 2.2 VI = 20 mA
R = Ω
2.Easy
+−Vs​5 VR = 2.2 kΩD​I = ?

A 5 V DC source drives current through a 2.2 kΩ resistor in series with a forward-biased silicon diode. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 5 VR = 2.2 kΩVD = 0.7 V
I = mA
3.Medium
+−12 V150 Ω3.3 V470 ΩIZ​ = ?

A 3.3 V Zener regulator is fed from 12 V through 150 Ω and supplies a 470 Ω load. Find the Zener current IZ.

Vin = 12 VVZ = 3.3 VR = 150 ΩRL = 470 Ω
IZ = mA
4.Medium
RC​ = 1.5 kΩβ = 100IC​ = ?VCC​ = 12 VRB​ = 680 kΩ

An NPN transistor with β = 100 is biased by a base resistor RB = 680 kΩ from the supply VCC = 12 V. The collector resistor is RC = 1.5 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 = 12 VRB = 680 kΩRC = 1.5 kΩβ = 100VBE = 0.7 V
IC = mA
5.Hard
+−≥ 20 VR = ?3.3 V≤ 20 mA

A 3.3 V Zener regulator must supply up to 20 mA to a load. The input can drop to 20 V, and the Zener needs at least 5 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 20 VVZ = 3.3 VIL,max = 20 mAIZ,min = 5 mA
Rmax = Ω
6.Hard
+−≤ 26 V330 Ω9.1 V

A 9.1 V Zener regulator has a 330 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 = 9.1 VR = 330 Ω
PZ,max = mW

Answer key

  1. 1. R = 490 Ω
  2. 2. I = 1.955 mA
  3. 3. IZ = 50.98 mA
  4. 4. IC = 1.662 mA
  5. 5. Rmax = 668 Ω
  6. 6. PZ,max = 466 mW

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