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​3 VR = 4.7 kΩD​I = ?

A 3 V DC source drives current through a 4.7 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 = 3 VR = 4.7 kΩVD = 0.7 V
I = mA
2.Easy
+−24 VR = ?3 V5 mA

A white LED with a forward voltage of 3 V runs from a 24 V supply through a series resistor. Find the resistance R that sets the LED current to 5 mA.

Vs = 24 VVF = 3 VI = 5 mA
R = Ω
3.Medium
RC​ = 4.7 kΩβ = 150IC​ = ?VCC​ = 12 VRB​ = 1000 kΩ

An NPN transistor with β = 150 is biased by a base resistor RB = 1000 kΩ from the supply VCC = 12 V. The collector resistor is RC = 4.7 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 = 12 VRB = 1000 kΩRC = 4.7 kΩβ = 150VBE = 0.7 V
IC = mA
4.Medium
+−9 V220 Ω6.2 V2200 ΩIZ​ = ?

A 6.2 V Zener regulator is fed from 9 V through 220 Ω and supplies a 2200 Ω load. Find the Zener current IZ.

Vin = 9 VVZ = 6.2 VR = 220 ΩRL = 2200 Ω
IZ = mA
5.Hard
V (V)I (mA)0.651212Q = ?

A diode is modelled as 0.65 V in series with 10 Ω (it conducts above 0.65 V). It is in series with a 1000 Ω resistor across a 12 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 12 VR = 1000 ΩV0 = 0.65 Vrd = 10 Ω
ID = mA
6.Hard
RC​ = 220 Ωβ = 100VCC​ = 9 V3.3 VRB​ = ?

An NPN transistor with β = 100 switches a 220 Ω load resistor connected between VCC = 9 V and its collector. The emitter is grounded. The base is driven from a 3.3 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 10 times the minimum needed for saturation. Find RB in kΩ.

VCC = 9 VRC = 220 Ωβ = 100Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 10
RB = kΩ

Answer key

  1. 1. I = 0.4894 mA
  2. 2. R = 4200 Ω
  3. 3. IC = 1.695 mA
  4. 4. IZ = 9.909 mA
  5. 5. ID = 11.24 mA
  6. 6. RB = 0.65 kΩ

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