Doubling coil current

[sled]

Just came along this interesting article about how to double the current in the coil of a LC tank. I like the idea because it increases the coil's resistance four times without affecting the Q factor while doubling the current in the coil. This is particularly useful as it transforms coils from the 2-8 ohm range to the 8-32 ohm range, easier to find a good audio amplifier IC in that region.

[homefire]

The L/R components comprise a Low Pass Filter limiting your band width.

[sled]

the R is the parasitic resistance of the coil, will be there any way :/

[Carl-NC]

There's no free lunch here. This is a case of splitting the tank cap and putting part of it in series with the drive signal. Yes, it seemingly boosts the coil current, but strictly at the expense of more drive current.

Look at it this way... if CS=0 and R -> 0 then almost all of the coil current is recirculated through the tank cap CP, and almost none of it is provided by the driver. You could easily find that such a circuit "amplifies" the drive current by a factor of 100! That's way better than just doubling the current.

The circuit shown is an impedance transformer (as stated) and is useful in optimizing the drive of the amplifier but it doesn't magically double the coil current at no cost. Besides that, most detector TX drivers are current-mode, not voltage mode. You could drive with a voltage driver but I suspect it's less efficient for the normal parameters of detector design (even with an optimized drive impedance), otherwise it would be the overwhelming circuit of choice.

[kt315]

you can easely get 10...20A peak coil current in pulse induction encreasing PULSE WIDTH.
or? what current value/range you mean???
read DELTA PULSE http://www.geotech1.com/forums/showt...03-Delta-Pulse

[sled]

There's no free lunch here. This is a case of splitting the tank cap and putting part of it in series with the drive signal. Yes, it seemingly boosts the coil current, but strictly at the expense of more drive current.

Look at it this way... if CS=0 and R -> 0 then almost all of the coil current is recirculated through the tank cap CP, and almost none of it is provided by the driver. You could easily find that such a circuit "amplifies" the drive current by a factor of 100! That's way better than just doubling the current.

The circuit shown is an impedance transformer (as stated) and is useful in optimizing the drive of the amplifier but it doesn't magically double the coil current at no cost. Besides that, most detector TX drivers are current-mode, not voltage mode. You could drive with a voltage driver but I suspect it's less efficient for the normal parameters of detector design (even with an optimized drive impedance), otherwise it would be the overwhelming circuit of choice.

You're right of course. I wonder if this impedance transformer brings any benefits when using an (audio) amplifier IC such as the LM4890? Those ICs are usually not specified for impedances below 8 ohms. With the proposed circuit, the impedance seen by the amplifier is four times the coil's DC resistance. This puts the impedance seen by the amplifier in its operating range (8-32 Ohms) for most coils.

[sled]

you can easely get 10...20A peak coil current in pulse induction encreasing PULSE WIDTH.
or? what current value/range you mean???
read DELTA PULSE http://www.geotech1.com/forums/showt...03-Delta-Pulse

It's for a VLF detector

[homefire]

Are you thinking of using one on the Tx coil ? Confused here.

[sled]

Are you thinking of using one on the Tx coil ? Confused here.

Yes it's about driving the transmit coil

[bernte_one]

hello sled pls watch you notifications

[kt315]

It's for a VLF detector

what you say the new absolutely is not new. Jurij Petrik had made this type TX detectors, VLFs.
i give you only one his schema as example.