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​15 VR1​ = 680 ΩR2​ = 2.2 kΩID​ = ?

A 15 V DC source is connected through resistor R₁ = 680 Ω to a node X. From node X to the source’s negative terminal there are two parallel paths: resistor R₂ = 2.2 kΩ, and a silicon diode with its anode at X. Use the constant-drop model with 0.7 V. Find the diode current ID in mA.

Vs = 15 VR1 = 680 ΩR2 = 2.2 kΩVD = 0.7 V
ID = mA
2.Easy
+−18 V100 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 18 V through a 100 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 18 VVZ = 6.2 VR = 100 Ω
IR = mA
3.Medium
+−24 V470 Ω5.1 V680 ΩIZ​ = ?

A 5.1 V Zener regulator is fed from 24 V through 470 Ω and supplies a 680 Ω load. Find the Zener current IZ.

Vin = 24 VVZ = 5.1 VR = 470 ΩRL = 680 Ω
IZ = mA
4.Medium
+−12 VR = ?4 × 2 V25 mA

4 red LEDs (forward voltage 2 V each) are connected in series with a resistor to a 12 V supply. Find the resistance R that sets the current to 25 mA.

Vs = 12 VVF = 2 Vn = 4I = 25 mA
R = Ω
5.Hard
RC​ = 1 kΩβ = 150IC​ = ?VCC​ = 5 V3.3 VRB​ = 33 kΩ

An NPN transistor with β = 150 switches a 1 kΩ 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 = 33 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 = 5 VRC = 1 kΩβ = 150Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 33 kΩ
IC = mA
6.Hard
V (V)I (mA)0.7515.15Q = ?

A diode is modelled as 0.7 V in series with 20 Ω (it conducts above 0.7 V). It is in series with a 330 Ω resistor across a 5 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 5 VR = 330 ΩV0 = 0.7 Vrd = 20 Ω
ID = mA

Answer key

  1. 1. ID = 20.71 mA
  2. 2. IR = 118 mA
  3. 3. IZ = 32.71 mA
  4. 4. R = 160 Ω
  5. 5. IC = 4.8 mA
  6. 6. ID = 12.29 mA

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