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
+−24 V150 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 24 V through a 150 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 24 VVZ = 6.2 VR = 150 Ω
IR = mA
2.Easy
+−24 VR = ?2 V10 mA

A red LED with a forward voltage of 2 V runs from a 24 V supply through a series resistor. Find the resistance R that sets the LED current to 10 mA.

Vs = 24 VVF = 2 VI = 10 mA
R = Ω
3.Medium
+−12 VR = ?2 × 2.2 V15 mA

2 green LEDs (forward voltage 2.2 V each) are connected in series with a resistor to a 12 V supply. Find the resistance R that sets the current to 15 mA.

Vs = 12 VVF = 2.2 Vn = 2I = 15 mA
R = Ω
4.Medium
RC​ = 3.3 kΩβ = 120IC​ = ?VCC​ = 9 VRB​ = 820 kΩ

An NPN transistor with β = 120 is biased by a base resistor RB = 820 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 current IC in mA.

VCC = 9 VRB = 820 kΩRC = 3.3 kΩβ = 120VBE = 0.7 V
IC = mA
5.Hard
V (V)I (mA)0.65522.73Q = ?

A diode is modelled as 0.65 V in series with 5 Ω (it conducts above 0.65 V). It is in series with a 220 Ω resistor across a 5 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 5 VR = 220 ΩV0 = 0.65 Vrd = 5 Ω
ID = mA
6.Hard
RC​ = 330 Ωβ = 150IC​ = ?VCC​ = 12 V3.3 VRB​ = 1 kΩ

An NPN transistor with β = 150 switches a 330 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 = 1 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 = 12 VRC = 330 Ωβ = 150Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 1 kΩ
IC = mA

Answer key

  1. 1. IR = 118.7 mA
  2. 2. R = 2200 Ω
  3. 3. R = 506.7 Ω
  4. 4. IC = 1.215 mA
  5. 5. ID = 19.33 mA
  6. 6. IC = 35.76 mA

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