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​5 VR = 220 ΩD1​D2​I = ?

A 5 V DC source drives current through a 220 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 = 5 VR = 220 ΩVD = 0.7 V
I = mA
2.Easy
+−Vs​24 VR = 1.5 kΩD​I = ?

A 24 V DC source drives current through a 1.5 kΩ 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 = 1.5 kΩVD = 0.7 V
I = mA
3.Medium
RC​ = 4.7 kΩβ = 150RE​ = 1.5 kΩVCC​ = 20 VR1​ = 68 kΩR2​ = 22 kΩ

An NPN transistor with β = 150 has voltage-divider bias from VCC = 20 V: R₁ = 68 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 = 1.5 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 = 68 kΩR2 = 22 kΩRC = 4.7 kΩRE = 1.5 kΩβ = 150
VCE = V
4.Medium
+−24 V680 Ω5.1 V1500 ΩIZ​ = ?

A 5.1 V Zener regulator is fed from 24 V through 680 Ω and supplies a 1500 Ω load. Find the Zener current IZ.

Vin = 24 VVZ = 5.1 VR = 680 ΩRL = 1500 Ω
IZ = mA
5.Hard
RC​ = 1 kΩβ = 100VCC​ = 24 V5 VRB​ = ?

An NPN transistor with β = 100 switches a 1 kΩ load resistor connected between VCC = 24 V and its collector. The emitter is grounded. The base is driven from a 5 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 = 24 VRC = 1 kΩβ = 100Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ
6.Hard
+−≥ 9 VR = ?5.1 V≤ 30 mA

A 5.1 V Zener regulator must supply up to 30 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 = 5.1 VIL,max = 30 mAIZ,min = 1 mA
Rmax = Ω

Answer key

  1. 1. I = 16.36 mA
  2. 2. I = 15.53 mA
  3. 3. VCE = 3.951 V
  4. 4. IZ = 24.39 mA
  5. 5. RB = 18.07 kΩ
  6. 6. Rmax = 125.8 Ω

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