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
+−20 V220 Ω5.1 VIR​ = ?

A 5.1 V Zener diode is fed from 20 V through a 220 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 20 VVZ = 5.1 VR = 220 Ω
IR = mA
2.Easy
+−5 VR = ?3.2 V10 mA

A blue LED with a forward voltage of 3.2 V runs from a 5 V supply through a series resistor. Find the resistance R that sets the LED current to 10 mA.

Vs = 5 VVF = 3.2 VI = 10 mA
R = Ω
3.Medium
RC​ = 4.7 kΩβ = 120RE​ = 2.2 kΩVCC​ = 18 VR1​ = 33 kΩR2​ = 8.2 kΩ

An NPN transistor with β = 120 has voltage-divider bias from VCC = 18 V: R₁ = 33 kΩ from VCC to the base and R₂ = 8.2 kΩ from the base to ground. The collector resistor is RC = 4.7 kΩ and the emitter resistor is RE = 2.2 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 = 33 kΩR2 = 8.2 kΩRC = 4.7 kΩRE = 2.2 kΩβ = 120
VCE = V
4.Medium
RC​ = 2.2 kΩβ = 80VCC​ = 9 VRB​ = 330 kΩ

An NPN transistor with β = 80 is biased by a base resistor RB = 330 kΩ from the supply VCC = 9 V. The collector resistor is RC = 2.2 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 = 9 VRB = 330 kΩRC = 2.2 kΩβ = 80VBE = 0.7 V
VCE = V
5.Hard
RC​ = 220 Ωβ = 150VCC​ = 5 V5 VRB​ = ?

An NPN transistor with β = 150 switches a 220 Ω load resistor connected between VCC = 5 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 = 5 VRC = 220 Ωβ = 150Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ
6.Hard
+−≥ 24 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 24 V, and the Zener needs at least 5 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 24 VVZ = 3.3 VIL,max = 10 mAIZ,min = 5 mA
Rmax = Ω

Answer key

  1. 1. IR = 67.73 mA
  2. 2. R = 180 Ω
  3. 3. VCE = 9.227 V
  4. 4. VCE = 4.573 V
  5. 5. RB = 29.56 kΩ
  6. 6. Rmax = 1380 Ω

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