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I need a suggestion about a reulator for DTMF

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EOJ

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DTMF

I have built these circuts and all I have is a 9v batt. I need it dropped down to 5v. How is the best way to do this. Pot, linear reg? if linear does anybody have a specific part number? Any help would be great! Thanks
 

Diver300

Well-Known Member
Most Helpful Member
You need 5 V for the circuit. A regulator will reduce the battery voltage down to 5 V and it doesn't matter what the battery voltage is.

However, there are limits. The lower limit is the above 5 V, and the amount that it is above 5 V is called the "drop out" voltage. A standard regulator has a drop out of about 2 V so you would need at least 7 V on the battery to maintain 5 V.

That doesn't seem so bad with a 9 V battery, but in fact 9V batteries will soon drop below 9 V when used, and a lot more current can be got out after that, but the voltage will continue to fall. After about 6 V there isn't much left.

If you use a low drop regulator, you will still get 5 V out when the battery is down to 5.5 V so you will get more out of the battery.
 

EOJ

Member
OK I gotcha thanks for explaining that to me. I was recommended from someone else about getting a linear regulator. What are your thoughts on that? Did you check out the link on the original post?
 

Hero999

Banned
The LM7805 will work, but it'll stop regulating when the voltage drop below 7V (6.5V on light loads) so the battery won't last as long compared to a low drop-out regulator.
 

shimniok

Member
been digging into regulators recently... and discovered that there's a tradeoff with LDO regulators possibly requiring more quiescent current than other types, which could impact battery life if you have a circuit (IR remote control extender/repeater) that sits around in standby most of the time. Just a thought... A more efficient option, it seems, would be a switching regulator...
 

Hero999

Banned
That's why the LM2936Z-5 exists, just a quiescent current of just 15µA.
 
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