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 V10 mA

A red LED with a forward voltage of 2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 10 mA.

Vs = 12 VVF = 2 VI = 10 mA
R = Ω
2.Easy
+−Vs​24 VR = 220 ΩD​I = ?

A 24 V DC source drives current through a 220 Ω 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 = 24 VR = 220 ΩVD = 0.7 V
I = mA
3.Medium
+−24 V270 Ω9.1 V1000 ΩIZ​ = ?

A 9.1 V Zener regulator is fed from 24 V through 270 Ω and supplies a 1000 Ω load. Find the Zener current IZ.

Vin = 24 VVZ = 9.1 VR = 270 ΩRL = 1000 Ω
IZ = mA
4.Medium
RC​ = 1.5 kΩβ = 80VCC​ = 15 VRB​ = 560 kΩ

An NPN transistor with β = 80 is biased by a base resistor RB = 560 kΩ from the supply VCC = 15 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–emitter voltage VCE.

VCC = 15 VRB = 560 kΩRC = 1.5 kΩβ = 80VBE = 0.7 V
VCE = V
5.Hard
RC​ = 220 Ωβ = 80VCC​ = 9 V3.3 VRB​ = ?

An NPN transistor with β = 80 switches a 220 Ω load resistor connected between VCC = 9 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. For reliable switching, design for a base current 5 times the minimum needed for saturation. Find RB in kΩ.

VCC = 9 VRC = 220 Ωβ = 80Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 5
RB = kΩ
6.Hard
+−≥ 20 VR = ?5.6 V≤ 10 mA

A 5.6 V Zener regulator must supply up to 10 mA to a load. The input can drop to 20 V, and the Zener needs at least 1 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 20 VVZ = 5.6 VIL,max = 10 mAIZ,min = 1 mA
Rmax = Ω

Answer key

  1. 1. R = 1000 Ω
  2. 2. I = 105.9 mA
  3. 3. IZ = 46.09 mA
  4. 4. VCE = 11.94 V
  5. 5. RB = 1.04 kΩ
  6. 6. Rmax = 1309 Ω

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