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 VR1​ = 680 ΩR2​ = 1.5 kΩID​ = ?

A 15 V DC source is connected through resistor R₁ = 680 Ω to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 1.5 kΩ, and a silicon diode with its anode at X. Use the constant-drop model with 0.7 V. Find the diode current ID in mA.

Vs = 15 VR1 = 680 ΩR2 = 1.5 kΩVD = 0.7 V
ID = mA
2.Easy
+−Vs​10 VR1​ = 680 ΩR2​ = 3.3 kΩID​ = ?

A 10 V DC source is connected through resistor R₁ = 680 Ω to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 3.3 kΩ, and a silicon diode with its anode at X. Use the constant-drop model with 0.7 V. Find the diode current ID in mA.

Vs = 10 VR1 = 680 ΩR2 = 3.3 kΩVD = 0.7 V
ID = mA
3.Medium
RC​ = 4.7 kΩβ = 80RE​ = 680 ΩVCC​ = 18 VR1​ = 100 kΩR2​ = 22 kΩ

An NPN transistor with β = 80 has voltage-divider bias from VCC = 18 V: R₁ = 100 kΩ from VCC to the base and R₂ = 22 kΩ from the base to ground. The collector resistor is RC = 4.7 kΩ and the emitter resistor is RE = 680 Ω. 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 = 18 VR1 = 100 kΩR2 = 22 kΩRC = 4.7 kΩRE = 680 Ωβ = 80
VCE = V
4.Medium
RC​ = 1 kΩβ = 100RE​ = 680 ΩVCC​ = 20 VR1​ = 39 kΩR2​ = 15 kΩ

An NPN transistor with β = 100 has voltage-divider bias from VCC = 20 V: R₁ = 39 kΩ from VCC to the base and R₂ = 15 kΩ from the base to ground. The collector resistor is RC = 1 kΩ and the emitter resistor is RE = 680 Ω. 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 = 39 kΩR2 = 15 kΩRC = 1 kΩRE = 680 Ωβ = 100
VCE = V
5.Hard
+−≥ 9 VR = ?3.3 V≤ 10 mA

A 3.3 V Zener regulator must supply up to 10 mA to a load. The input can drop to 9 V, and the Zener needs at least 1 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 9 VVZ = 3.3 VIL,max = 10 mAIZ,min = 1 mA
Rmax = Ω
6.Hard
RC​ = 220 Ωβ = 50VCC​ = 12 V3.3 VRB​ = ?

An NPN transistor with β = 50 switches a 220 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. Take VBE = 0.7 V and VCE(sat) = 0.2 V. Find the largest base resistor RB, in kΩ, that still drives the transistor just into saturation.

VCC = 12 VRC = 220 Ωβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ

Answer key

  1. 1. ID = 20.56 mA
  2. 2. ID = 13.46 mA
  3. 3. VCE = 2.989 V
  4. 4. VCE = 9.699 V
  5. 5. Rmax = 518.2 Ω
  6. 6. RB = 2.424 kΩ

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