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​10 VR = 1.5 kΩD​I = ?

A 10 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 = 10 VR = 1.5 kΩVD = 0.7 V
I = mA
2.Easy
+−Vs​5 VR = 330 ΩD​I = ?

A 5 V DC source drives current through a 330 Ω 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 = 5 VR = 330 ΩVD = 0.7 V
I = mA
3.Medium
+−24 VR = ?5 × 3 V25 mA

5 white LEDs (forward voltage 3 V each) are connected in series with a resistor to a 24 V supply. Find the resistance R that sets the current to 25 mA.

Vs = 24 VVF = 3 Vn = 5I = 25 mA
R = Ω
4.Medium
+−12 V270 Ω6.2 V1500 ΩIZ​ = ?

A 6.2 V Zener regulator is fed from 12 V through 270 Ω and supplies a 1500 Ω load. Find the Zener current IZ.

Vin = 12 VVZ = 6.2 VR = 270 ΩRL = 1500 Ω
IZ = mA
5.Hard
RC​ = 680 Ωβ = 200VCC​ = 9 V5 VRB​ = ?

An NPN transistor with β = 200 switches a 680 Ω load resistor connected between VCC = 9 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 = 9 VRC = 680 Ωβ = 200Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 2
RB = kΩ
6.Hard
V (V)I (mA)0.6618.18Q = ?

A diode is modelled as 0.6 V in series with 50 Ω (it conducts above 0.6 V). It is in series with a 330 Ω resistor across a 6 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 6 VR = 330 ΩV0 = 0.6 Vrd = 50 Ω
ID = mA

Answer key

  1. 1. I = 6.2 mA
  2. 2. I = 13.03 mA
  3. 3. R = 360 Ω
  4. 4. IZ = 17.35 mA
  5. 5. RB = 33.23 kΩ
  6. 6. ID = 14.21 mA

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