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
+−15 V330 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 15 V through a 330 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 15 VVZ = 6.2 VR = 330 Ω
IR = mA
2.Easy
+−9 VR = ?3.2 V5 mA

A blue LED with a forward voltage of 3.2 V runs from a 9 V supply through a series resistor. Find the resistance R that sets the LED current to 5 mA.

Vs = 9 VVF = 3.2 VI = 5 mA
R = Ω
3.Medium
+−18 V330 Ω12 V2200 ΩIZ​ = ?

A 12 V Zener regulator is fed from 18 V through 330 Ω and supplies a 2200 Ω load. Find the Zener current IZ.

Vin = 18 VVZ = 12 VR = 330 ΩRL = 2200 Ω
IZ = mA
4.Medium
RC​ = 3.3 kΩβ = 50VCC​ = 9 VRB​ = 1000 kΩ

An NPN transistor with β = 50 is biased by a base resistor RB = 1000 kΩ from the supply VCC = 9 V. The collector resistor is RC = 3.3 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 = 1000 kΩRC = 3.3 kΩβ = 50VBE = 0.7 V
VCE = V
5.Hard
RC​ = 150 Ωβ = 100IC​ = ?VCC​ = 24 V5 VRB​ = 4.7 kΩ

An NPN transistor with β = 100 switches a 150 Ω 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 = 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 = 24 VRC = 150 Ωβ = 100Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 4.7 kΩ
IC = mA
6.Hard
RC​ = 680 Ωβ = 100VCC​ = 5 V5 VRB​ = ?

An NPN transistor with β = 100 switches a 680 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. For reliable switching, design for a base current 2 times the minimum needed for saturation. Find RB in kΩ.

VCC = 5 VRC = 680 Ωβ = 100Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 2
RB = kΩ

Answer key

  1. 1. IR = 26.67 mA
  2. 2. R = 1160 Ω
  3. 3. IZ = 12.73 mA
  4. 4. VCE = 7.63 V
  5. 5. IC = 91.49 mA
  6. 6. RB = 30.46 kΩ

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