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​5 VR = 4.7 kΩD​I = ?

A 5 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 = 5 VR = 4.7 kΩVD = 0.7 V
I = mA
2.Easy
+−18 V470 Ω9.1 VIR​ = ?

A 9.1 V Zener diode is fed from 18 V through a 470 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 18 VVZ = 9.1 VR = 470 Ω
IR = mA
3.Medium
RC​ = 1 kΩβ = 100IC​ = ?RE​ = 1.2 kΩVCC​ = 12 VR1​ = 47 kΩR2​ = 22 kΩ

An NPN transistor with β = 100 has voltage-divider bias from VCC = 12 V: R₁ = 47 kΩ from VCC to the base and R₂ = 22 kΩ from the base to ground. The collector resistor is RC = 1 kΩ and the emitter resistor is RE = 1.2 kΩ. 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 = 12 VR1 = 47 kΩR2 = 22 kΩRC = 1 kΩRE = 1.2 kΩβ = 100
IC = mA
4.Medium
RC​ = 1.2 kΩβ = 100IC​ = ?VCC​ = 15 VRB​ = 390 kΩ

An NPN transistor with β = 100 is biased by a base resistor RB = 390 kΩ from the supply VCC = 15 V. The collector resistor is RC = 1.2 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 = 15 VRB = 390 kΩRC = 1.2 kΩβ = 100VBE = 0.7 V
IC = mA
5.Hard
RC​ = 220 Ωβ = 150VCC​ = 12 V3.3 VRB​ = ?

An NPN transistor with β = 150 switches a 220 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. 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 = 12 VRC = 220 Ωβ = 150Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 2
RB = kΩ
6.Hard
RC​ = 330 Ωβ = 80IC​ = ?VCC​ = 12 V5 VRB​ = 3.3 kΩ

An NPN transistor with β = 80 switches a 330 Ω load resistor connected between VCC = 12 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB = 3.3 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 = 80Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 VRB = 3.3 kΩ
IC = mA

Answer key

  1. 1. I = 0.9149 mA
  2. 2. IR = 18.94 mA
  3. 3. IC = 2.295 mA
  4. 4. IC = 3.667 mA
  5. 5. RB = 3.636 kΩ
  6. 6. IC = 35.76 mA

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