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​10 VR = 330 ΩD1​D2​I = ?

A 10 V DC source drives current through a 330 Ω 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 = 10 VR = 330 ΩVD = 0.7 V
I = mA
2.Easy
+−Vs​10 VR = 1 kΩD1​D2​I = ?

A 10 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 = 10 VR = 1 kΩVD = 0.7 V
I = mA
3.Medium
RC​ = 2.7 kΩβ = 80RE​ = 1.2 kΩVCC​ = 18 VR1​ = 56 kΩR2​ = 22 kΩ

An NPN transistor with β = 80 has voltage-divider bias from VCC = 18 V: R₁ = 56 kΩ from VCC to the base and R₂ = 22 kΩ from the base to ground. The collector resistor is RC = 2.7 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 = 18 VR1 = 56 kΩR2 = 22 kΩRC = 2.7 kΩRE = 1.2 kΩβ = 80
VCE = V
4.Medium
RC​ = 4.7 kΩβ = 120RE​ = 1 kΩVCC​ = 20 VR1​ = 22 kΩR2​ = 4.7 kΩ

An NPN transistor with β = 120 has voltage-divider bias from VCC = 20 V: R₁ = 22 kΩ from VCC to the base and R₂ = 4.7 kΩ from the base to ground. The collector resistor is RC = 4.7 kΩ and the emitter resistor is RE = 1 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 = 22 kΩR2 = 4.7 kΩRC = 4.7 kΩRE = 1 kΩβ = 120
VCE = V
5.Hard
RC​ = 1 kΩβ = 100IC​ = ?VCC​ = 9 V5 VRB​ = 10 kΩ

An NPN transistor with β = 100 switches a 1 kΩ load resistor connected between VCC = 9 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB = 10 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 = 1 kΩβ = 100Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 10 kΩ
IC = mA
6.Hard
RC​ = 150 Ωβ = 50VCC​ = 5 V3.3 VRB​ = ?

An NPN transistor with β = 50 switches a 150 Ω load resistor connected between VCC = 5 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 4 times the minimum needed for saturation. Find RB in kΩ.

VCC = 5 VRC = 150 Ωβ = 50Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 4
RB = kΩ

Answer key

  1. 1. I = 26.06 mA
  2. 2. I = 8.6 mA
  3. 3. VCE = 5.868 V
  4. 4. VCE = 4.527 V
  5. 5. IC = 8.8 mA
  6. 6. RB = 1.016 kΩ

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