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​15 VR = 1.5 kΩD1​D2​I = ?

A 15 V DC source drives current through a 1.5 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 = 15 VR = 1.5 kΩVD = 0.7 V
I = mA
2.Easy
+−9 V680 Ω5.1 VIR​ = ?

A 5.1 V Zener diode is fed from 9 V through a 680 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 9 VVZ = 5.1 VR = 680 Ω
IR = mA
3.Medium
+−9 V330 Ω3.3 V680 ΩIZ​ = ?

A 3.3 V Zener regulator is fed from 9 V through 330 Ω and supplies a 680 Ω load. Find the Zener current IZ.

Vin = 9 VVZ = 3.3 VR = 330 ΩRL = 680 Ω
IZ = mA
4.Medium
RC​ = 3.3 kΩβ = 100RE​ = 1.2 kΩVCC​ = 20 VR1​ = 82 kΩR2​ = 22 kΩ

An NPN transistor with β = 100 has voltage-divider bias from VCC = 20 V: R₁ = 82 kΩ from VCC to the base and R₂ = 22 kΩ from the base to ground. The collector resistor is RC = 3.3 kΩ and the emitter resistor is RE = 1.2 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 = 82 kΩR2 = 22 kΩRC = 3.3 kΩRE = 1.2 kΩβ = 100
VCE = V
5.Hard
RC​ = 150 Ωβ = 50IC​ = ?VCC​ = 9 V3.3 VRB​ = 4.7 kΩ

An NPN transistor with β = 50 switches a 150 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 = 4.7 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 = 9 VRC = 150 Ωβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 4.7 kΩ
IC = mA
6.Hard
+−≥ 15 VR = ?9.1 V≤ 25 mA

A 9.1 V Zener regulator must supply up to 25 mA to a load. The input can drop to 15 V, and the Zener needs at least 5 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 15 VVZ = 9.1 VIL,max = 25 mAIZ,min = 5 mA
Rmax = Ω

Answer key

  1. 1. I = 9.067 mA
  2. 2. IR = 5.735 mA
  3. 3. IZ = 12.42 mA
  4. 4. VCE = 8.501 V
  5. 5. IC = 27.66 mA
  6. 6. Rmax = 196.7 Ω

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