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 = 1 kΩD1​D2​I = ?

A 9 V DC source drives current through a 1 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 = 1 kΩVD = 0.7 V
I = mA
2.Easy
+−9 VR = ?2.1 V10 mA

A yellow LED with a forward voltage of 2.1 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 = 2.1 VI = 10 mA
R = Ω
3.Medium
RC​ = 3.3 kΩβ = 100RE​ = 1.5 kΩVCC​ = 20 VR1​ = 47 kΩR2​ = 8.2 kΩ

An NPN transistor with β = 100 has voltage-divider bias from VCC = 20 V: R₁ = 47 kΩ from VCC to the base and R₂ = 8.2 kΩ from the base to ground. The collector resistor is RC = 3.3 kΩ and the emitter resistor is RE = 1.5 kΩ. 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 = 20 VR1 = 47 kΩR2 = 8.2 kΩRC = 3.3 kΩRE = 1.5 kΩβ = 100
VCE = V
4.Medium
RC​ = 1 kΩβ = 150IC​ = ?VCC​ = 10 VRB​ = 470 kΩ

An NPN transistor with β = 150 is biased by a base resistor RB = 470 kΩ from the supply VCC = 10 V. The collector resistor is RC = 1 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 = 1 kΩβ = 150VBE = 0.7 V
IC = mA
5.Hard
+−≤ 19 V150 Ω12 V

A 12 V Zener regulator has a 150 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 = 12 VR = 150 Ω
PZ,max = mW
6.Hard
V (V)I (mA)0.633Q = ?

A diode is modelled as 0.6 V in series with 10 Ω (it conducts above 0.6 V). It is in series with a 1000 Ω resistor across a 3 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 3 VR = 1000 ΩV0 = 0.6 Vrd = 10 Ω
ID = mA

Answer key

  1. 1. I = 7.6 mA
  2. 2. R = 690 Ω
  3. 3. VCE = 13.1 V
  4. 4. IC = 2.968 mA
  5. 5. PZ,max = 560 mW
  6. 6. ID = 2.376 mA

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