i know that a diode allows electron flow in a single direction.But doesn't this happen in a circuit even without a diode (for dc source). then why do we need a diode.
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2$\begingroup$ Maybe your circuit needs a diode. Maybe it doesn't. Diodes can do many things, of which rectification is but one. $\endgroup$– Jon CusterCommented Nov 21, 2015 at 0:41
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3$\begingroup$ Would Electrical Engineering be a better home for this question? $\endgroup$– Qmechanic ♦Commented Nov 21, 2015 at 0:49
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1$\begingroup$ Perhaps a better suggestion would be to suggest the OP do a bit of basic online research before posting such a question & wasting everyone's time for answers that can easily be obtain by Googling "diode functions in a circuit". The top 2 hits would be MORE than adequate to answer the OPs question. $\endgroup$– DIYserCommented Nov 21, 2015 at 0:59
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2 Answers
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Even in a 'DC' circuit, diodes can be useful for, e.g., current steering.
Consider a rudimentary battery backup system:
When the primary 14V supply is present, the LED is on while D2 and R2 prevent the battery from charging at too high a current.
When the primary 14V supply isn't present, D1 'disconnects' the LED and regulator IC from the battery while D2 allows the battery to discharge through the load.
There are many applications for diodes including mixing, temperature sensing, over-voltage protection, and voltage controlled capacitance to name just a few.
In short, there are many applications for diodes as can be sampled here
answered Nov 21, 2015 at 1:26
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i know that a diode allows electron flow in a single direction.But doesn't this happen in a circuit even without a diode (for dc source). then why do we need a diode.
A diode has the miraculous property of allowing the current to flow only in a single direction even if an AC source is used.
