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​12 VR = 3.3 kΩD1​D2​I = ?

A 12 V DC source drives current through a 3.3 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 = 12 VR = 3.3 kΩVD = 0.7 V
I = mA
2.Easy
+−Vs​9 VR = 2.2 kΩD1​D2​I = ?

A 9 V DC source drives current through a 2.2 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 = 2.2 kΩVD = 0.7 V
I = mA
3.Medium
+−20 V150 Ω5.6 V1000 ΩIZ​ = ?

A 5.6 V Zener regulator is fed from 20 V through 150 Ω and supplies a 1000 Ω load. Find the Zener current IZ.

Vin = 20 VVZ = 5.6 VR = 150 ΩRL = 1000 Ω
IZ = mA
4.Medium
+−24 VR = ?2 × 2 V15 mA

2 red LEDs (forward voltage 2 V each) are connected in series with a resistor to a 24 V supply. Find the resistance R that sets the current to 15 mA.

Vs = 24 VVF = 2 Vn = 2I = 15 mA
R = Ω
5.Hard
RC​ = 680 Ωβ = 80IC​ = ?VCC​ = 12 V3.3 VRB​ = 3.3 kΩ

An NPN transistor with β = 80 switches a 680 Ω 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 = 3.3 kΩ. Take VBE = 0.7 V and VCE(sat) = 0.2 V. Find the collector current IC in mA when the input is high. Decide first whether the transistor is saturated.

VCC = 12 VRC = 680 Ωβ = 80Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 3.3 kΩ
IC = mA
6.Hard
+−≤ 26 V150 Ω6.2 V

A 6.2 V Zener regulator has a 150 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 = 6.2 VR = 150 Ω
PZ,max = mW

Answer key

  1. 1. I = 3.212 mA
  2. 2. I = 3.455 mA
  3. 3. IZ = 90.4 mA
  4. 4. R = 1333 Ω
  5. 5. IC = 17.35 mA
  6. 6. PZ,max = 818.4 mW

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