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In a Zener regulated power supply a Zener diode with V_(z)= 6.0 Vis used forregulation. The load current is to be 4.0 mA and the unregulated input is 10.0 V. What should be the value of series resistorR_(s)? |
| Answer» SOLUTION :The value of`R_(s)` should be such that the current through the Zener diode is much larger thanthe load current. This is tohave goodload regulation. Choose Zener current as five times the load current. This is to have good load regulation. Choose Zener current as five TIMESTHE load current, i.e., `I_(Z) = 20 mA`. The total current through `R_(S)` is therefore 24mA.The voltage drop across`R_(S)`is `10.0- 6.0 =4.0 V`.This gives `R_(S) = 4.0 V ( 24 xx 10^(-3) )A167 Omega `.The nearest value of CARBON resistoris `150 Omega `. So, a seriesof `150 Omega ` is appropriate . NOTE that slight variationin the value of the resistordoes not matter, what is important is that the current `I_(Z)` should be sufficiently larger than `I_(L)`. | |