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

A yellow LED with a forward voltage of 2.1 V runs from a 24 V supply through a series resistor. Find the resistance R that sets the LED current to 15 mA.

V_s = 24 VV_F = 2.1 VI = 15 mA

R = Ω

2.Easy

A green LED with a forward voltage of 2.2 V runs from a 12 V supply through a series resistor. Find the resistance R that sets the LED current to 20 mA.

V_s = 12 VV_F = 2.2 VI = 20 mA

R = Ω

3.Medium

A 5.6 V Zener regulator is fed from 24 V through 680 Ω and supplies a 2200 Ω load. Find the Zener current I_Z.

V_in = 24 VV_Z = 5.6 VR = 680 ΩR_L = 2200 Ω

I_Z = mA

4.Medium

An NPN transistor with β = 50 is biased by a base resistor R_B = 220 kΩ from the supply V_CC = 15 V. The collector resistor is R_C = 1.2 kΩ and the emitter is grounded. Take V_BE = 0.7 V and assume the transistor is in the active region. Find the collector–emitter voltage V_CE.

V_CC = 15 VR_B = 220 kΩR_C = 1.2 kΩβ = 50V_BE = 0.7 V

V_CE = V

5.Hard

A 5.1 V Zener regulator has a 680 Ω series resistor. The input can rise to 17 V, and the load may be disconnected. Find the largest power P_Z,max the Zener must dissipate.

V_in,max = 17 VV_Z = 5.1 VR = 680 Ω

P_Z,max = mW

6.Hard

A 6.2 V Zener regulator has a 220 Ω series resistor. The input can rise to 19 V, and the load may be disconnected. Find the largest power P_Z,max the Zener must dissipate.

V_in,max = 19 VV_Z = 6.2 VR = 220 Ω

P_Z,max = mW

Answer key

1. R = 1460 Ω
2. R = 490 Ω
3. I_Z = 24.51 mA
4. V_CE = 11.1 V
5. P_Z,max = 89.25 mW
6. P_Z,max = 360.7 mW

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