Looking for a Simple Current Doubler Curcuit???

Hi Folks, I am looking for a Simple Current Doubling Curcuit (Voltage Halving??) as I am trying to design a opamp Based Microphone design powered off of Phantom power but I would Like to get the 48V down to 12V-24V and get the 14ma current up to 30 - 60ma to run the Opamp....

I have found many Voltage doubling curcuits but Current doubleing seems like it would be the Opposite Concept of Voltage doubleing.....

I would like to use as Few components as reasonably possible.....

Thanx a Lot Folks.....

Cheers

if you load phantom power with 14ma voltage will go down right by itself to nothing. no way to load it with more - but someone correct me if i am wrong.

If your PSU will supply the current, there is no need to worry about a "current doubler". I dont think anything like this exists, but I could be wrong.... :?

If your Phantom supply wont provide enough current, then there is no way to "double" this.

If you want to run this mic pre of yours from a desk, there should be enough current, tho'. Most manufacturers allow at least 10mA per channel, so for an 8 channel desk, there should be about 80mA or more available.

Select the opamps for lower power as well. For e.g. you wouldnt use a 5532 or 5534 in there, they are notorious current hogs.... No sure what to use for a less hungry opamp tho.

Peter

We can double V, at the expence of I.
For the same given P we can double I at the expence of V.

This has to be done at the source, your power transformer.

We can not transform P.

I did find some Cuircuts that double current at the expense of Voltage but they were Fairly complicated which I can"t use in a small Mic curcuit...

If you think that there should be enough Current for a Low power opamp then I"ll give it a shot...

ThanX

Yes, you can increase the current by stepping down the volts using switching circuits. There was a recent thread about this in relation to the AT3060 and a Japanese patent: http://www.groupdiy.com/index.php?topic=16934&highlight=at3060
You might get 20mA at 10V using two voltage-halving circuits.

However, there are two points to note:
(1) 48V phantom power is supplied via 6K8 resistors in each leg.
(2) as a corollary of (1), 14mA is the raw short-circuit current. No volts are available if you take this current.

You might also care to look at this DI box design: http://users.adelphia.net/~thomasholley/Guitar/Mini Tube DI.gif

By the conjugate matching theorem the most you can draw out of 48V with 3.4k (the two paralleled 6.8k's) in series will be with a conjugate load, which in this purely resistive case is simply 3.4k---and you wind up with 24V at about 7.1mA, or a maximum power of 169mW. The power developed across an open and a short is the same: zero.

And as Boswell points out, optimally switching converter techniques should be used to approach that maximum power, subject to the limitation of the matching and losses in the converter.

So with normal phantom power there is no way to get to your 30-60mA @ 24V (0.72 to 1.44 W!)---but then you don't need that for most opamps anyway. What does the circuit look like? I'll bet you don't need anywhere near that much power.

I actually don"t really have a Curcuit yet, The first thing I wanted to tackle was getting enough currect to run an opamp because if I could not do that there was really no use in trying to design a curcuit.....

Thanx guys, I guess I have some stuff to look in to.....


Cheers

Are you looking for a free design?

there are opamp based microphones lets see the fet47.............................

Yes, If you know of any free Mic designs i would love to look at them....The thing is I will probably be useing a modified Electret Capsule so I need a design that either uses this type of Capsule or can be easilly modified to use this type of Capsule....

I have Made Many Mics before and even designed a couple curcuits but I figured since I have like 50 opamps of about 10 different Types that I would try an opamp based Mic curcuit.....

If you know of any opamp Mic curcuits I would be very thankfull if you could post a link....

Thanx a Lot...

Cheers

Hmmmm, in my mind an opamp-based mic has no advantage over a discrete design. Maybe parts cost, but that won't be more than a few dollars. If you want a nice, simple electret capsule mic circuit, check Scott "scodiddly" Helmke's.

I have found a application sheet of BB with opa2604 making up to 70mA of output power with up to 48V.
Just have a look there.