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What is a Zener diode ? Explain how it is used as a voltage regulator . |
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Answer» Solution :Zener diode `:` Zener diode is a heavily doped germanium (or) silicon p-n JUNCTION diode. It words on reverse bias break down region. The circuit symbol of zener diode is shown in figure.  Zener diode can be used as a voltage regulator. In generalzener diodeis connected in reverse bias in the circuits.  (i) The Zener diode is connected to a battery,through a resistance R.The battery reverse BIASES the zener diode. (ii) The load resistance `R_(L)` is connected across the terminals of the zener diode. (iii) The value of R is selected in such away that in the absenceof load `R_(L)` maximum safe current flows in the diode. (iv) Now consider that load is connected across the diode. The load draws a current. (v) Thecurrent through the diode falls by the same amount but the voltage drops across the load remains constant. (vi) The series resistance 'R' absorbs the output voltage fluctuations, so as to maintain constant voltage across the load. (vii) The voltage across the zener diode remains constant even if the load `R_(L)` varies. Thus, zener diodeworkds as voltage regulator. (viii) If I is the INPUT current,`I_(Z)` and `I_(L)` are zener and load currents. `I= I_(Z) + I_(L), V_( i n) + IR +V_(Z)` But `V_(out) = V_(Z)` `:. V_(out) = V_( i n ) - IR ` |
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