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
+−Vs​9 VR = 4.7 kΩD1​D2​I = ?

A 9 V DC source drives current through a 4.7 kΩ resistor in series with two forward-biased silicon diodes. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 9 VR = 4.7 kΩVD = 0.7 V
I = mA
2.Easy
+−9 VR = ?2 V10 mA

A red LED with a forward voltage of 2 V runs from a 9 V supply through a series resistor. Find the resistance R that sets the LED current to 10 mA.

Vs = 9 VVF = 2 VI = 10 mA
R = Ω
3.Medium
RC​ = 4.7 kΩβ = 80IC​ = ?VCC​ = 10 VRB​ = 470 kΩ

An NPN transistor with β = 80 is biased by a base resistor RB = 470 kΩ from the supply VCC = 10 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 = 10 VRB = 470 kΩRC = 4.7 kΩβ = 80VBE = 0.7 V
IC = mA
4.Medium
+−15 V150 Ω3.3 V680 ΩIZ​ = ?

A 3.3 V Zener regulator is fed from 15 V through 150 Ω and supplies a 680 Ω load. Find the Zener current IZ.

Vin = 15 VVZ = 3.3 VR = 150 ΩRL = 680 Ω
IZ = mA
5.Hard
+−≤ 16 V220 Ω3.3 V

A 3.3 V Zener regulator has a 220 Ω series resistor. The input can rise to 16 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 16 VVZ = 3.3 VR = 220 Ω
PZ,max = mW
6.Hard
V (V)I (mA)0.65990Q = ?

A diode is modelled as 0.65 V in series with 20 Ω (it conducts above 0.65 V). It is in series with a 100 Ω resistor across a 9 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 9 VR = 100 ΩV0 = 0.65 Vrd = 20 Ω
ID = mA

Answer key

  1. 1. I = 1.617 mA
  2. 2. R = 700 Ω
  3. 3. IC = 1.583 mA
  4. 4. IZ = 73.15 mA
  5. 5. PZ,max = 190.5 mW
  6. 6. ID = 69.58 mA

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