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 VR = 1.5 kΩD1​D2​I = ?

A 15 V DC source drives current through a 1.5 kΩ resistor in series with two forward-biased silicon diodes. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 15 VR = 1.5 kΩVD = 0.7 V
I = mA
2.Easy
+−5 VR = ?3 V15 mA

A white LED with a forward voltage of 3 V runs from a 5 V supply through a series resistor. Find the resistance R that sets the LED current to 15 mA.

Vs = 5 VVF = 3 VI = 15 mA
R = Ω
3.Medium
RC​ = 2.7 kΩβ = 100IC​ = ?VCC​ = 12 VRB​ = 680 kΩ

An NPN transistor with β = 100 is biased by a base resistor RB = 680 kΩ from the supply VCC = 12 V. The collector resistor is RC = 2.7 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 = 680 kΩRC = 2.7 kΩβ = 100VBE = 0.7 V
IC = mA
4.Medium
RC​ = 3.3 kΩβ = 200IC​ = ?RE​ = 680 ΩVCC​ = 20 VR1​ = 39 kΩR2​ = 6.8 kΩ

An NPN transistor with β = 200 has voltage-divider bias from VCC = 20 V: R₁ = 39 kΩ from VCC to the base and R₂ = 6.8 kΩ from the base to ground. The collector resistor is RC = 3.3 kΩ and the emitter resistor is RE = 680 Ω. Take VBE = 0.7 V and use the Thévenin equivalent of the divider (do not neglect the base current). Find the collector current IC in mA.

VCC = 20 VR1 = 39 kΩR2 = 6.8 kΩRC = 3.3 kΩRE = 680 Ωβ = 200
IC = mA
5.Hard
RC​ = 330 Ωβ = 50VCC​ = 9 V5 VRB​ = ?

An NPN transistor with β = 50 switches a 330 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. Find the largest base resistor RB, in kΩ, that still drives the transistor just into saturation.

VCC = 9 VRC = 330 Ωβ = 50Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 V
RB = kΩ
6.Hard
+−≤ 22 V680 Ω3.3 V

A 3.3 V Zener regulator has a 680 Ω series resistor. The input can rise to 22 V, and the load may be disconnected. Find the largest power PZ,max the Zener must dissipate.

Vin,max = 22 VVZ = 3.3 VR = 680 Ω
PZ,max = mW

Answer key

  1. 1. I = 9.067 mA
  2. 2. R = 133.3 Ω
  3. 3. IC = 1.662 mA
  4. 4. IC = 3.186 mA
  5. 5. RB = 8.063 kΩ
  6. 6. PZ,max = 90.75 mW

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