Skip to main content

Zener circuit output voltage and current

Short answer

With Zener on, output voltage is 50V. Voltage drop across series resistance is 70V. Total current is 14mA, load current 5mA, so Zener current is 9mA.

For the circuit shown below, find: i) the output voltage ii) the voltage drop across series resistance iii) the current through Zener diode. [Figure: 120 V source in series with R=5 kΩR = 5\ k\Omega; Zener diode of 50 V in parallel with 10 kΩ load; II is total current, IZI_Z Zener current, ILI_L load current.]

Given: Vi=120V_i=120 V, R=5 kΩR=5\ \text{k}\Omega, VZ=50V_Z=50 V, RL=10 kΩR_L=10\ \text{k}\Omega.

Check Zener state. With the Zener removed, the load voltage is

VL=105+10×120=80 V>50 VV_L=\frac{10}{5+10}\times120=80\ \text{V}>50\ \text{V}

So the Zener is in breakdown (ON) and holds the load at 50 V.

(i) Output voltage:

Vo=VZ=50 VV_o=V_Z=50\ \text{V}

(ii) Voltage across the series resistance:

VR=120−50=70 VV_R=120-50=70\ \text{V}

(iii) Zener current.

I=VRR=705 kΩ=14 mAI=\frac{V_R}{R}=\frac{70}{5\ \text{k}\Omega}=14\ \text{mA} IL=5010 kΩ=5 mAI_L=\frac{50}{10\ \text{k}\Omega}=5\ \text{mA} IZ=I−IL=14−5=9 mAI_Z=I-I_L=14-5=9\ \text{mA}

Answer: (i) 50 V, (ii) 70 V, (iii) 9 mA (total current 14 mA, load current 5 mA).

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Basic Electrical and Electronics Engineering chapter 3 questions →