# What happens if you put two coils in parallel

I want to build an LC-Filter from a tutorial I found (German language, if anyone is interested, I'll add a link).

In that tutorial, a 330uH Coil with a max amp of 1A is used.
I have some 330uH coils lying around, but they've only 450mA.

The consumer device will draw up to 700mA.
Is it possible, to put the coils in parallel, like in that schematic?

For a better understanding, what exactly will happen if I do this? simulate this circuit – Schematic created using CircuitLab

• You can review en.wikipedia.org/wiki/Inductor and look at the section titled "Inductor networks" to see how both parallel and series combinations work. – Tyler Apr 28 '16 at 12:30
• Your solution is almost correct, you need to use two 660uH in parallel to make a 330uH equivalent. – lucas92 Apr 28 '16 at 12:44
• Since it's a copter application where every gram counts, I'd be tempted to benchmark your 450mA coil at 700mA. Chances are it won't overheat too much. – Dmitry Grigoryev Apr 28 '16 at 13:55

## 1 Answer

To make 330 uH from several 330 uH inductors requires, as a minimum, four devices - two in series gives 660 uH and then two parallel branches of two in series gives a net inductance of 330 uH.

It's just like resistors in parallel and series.

• Uhm,... so I'd better go with ordering the suitable coil, due it's meant to be light weight (FPV system on multicopter). But still, I learned something. Thank you! – Sempie Apr 28 '16 at 12:48