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Bifilar - Trifler transformer function in Amplification #5wPA
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timo.vandermerwe@...
Dear all,
On most class C and D amplifiers the IRF510 is followed by a trifilar or bifilar transformer toroid. Can someone please explain what the function of the this type of transformer is. (is it for impedance matching?) Google is just not providing me with a easy understandable answer. 73 Timo zr6tm |
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IMHO, the reason for trifilar is for tight coupling and balance between the windings. For when "close" isn't good enough! ;-) Paul On 1/29/23 22:54,
timo.vandermerwe@... wrote:
Dear all, |
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Dave VE3GSO
I presume, because your question is not sufficiently clear, that you are talking about a push pull amplifier, where a bifilar or two winding transformer is connected between the FET Drains and the power supply. Sometimes there is a third winding that serves as the output winding. Sometimes there is a separate transformer for the output impedance matching. The Bifilar Transformer serves to bring DC power to the drains and is a Push Pull transformer. One side will be going positive while th either side is pulled to ground by a conducting MOSFET. That make sense? Dave On Mon, Jan 30, 2023 at 1:54 AM <timo.vandermerwe@...> wrote: Dear all, |
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timo.vandermerwe@...
Thx Dave and Paul, Looking at the snip I agree that the bifilar winding 1 connects the 12v supply to the drain of the mosfet. Winding 1 then connects to Winding 2 to provide the PA output. Sorry for this uneducated question, but what function does the transformer perform in this instance. 73 Timo zr6tm |
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Hi Tim. In this case it is providing a 1:4 impedance step up from the 12.5 ohm FET Drain to 50 ohms at the input of the low pass filter. Ron On Mon, Jan 30, 2023 at 1:07 PM <timo.vandermerwe@...> wrote:
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timo.vandermerwe@...
Thx Ron,
Makes sense and is what I expected. So if bifilar provides a 1:4 impedance step, what would trifilar in the same configuration provide as a impedance step? 73 Timo zr6tm |
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Timo, It all depends on how the tri-filar is connected. It's just three parallel windings on a toroid. You could connect all three is series, tap one of the common points and get 9:1 or, you could tie two in series and leave the other separate and have two 1:1 with 180 degree phase difference or 4:1 with a center tap on the hi-z end.... Just about anything you want to do with it. So in the series connected try-filar, or the bi-filar windings case ike your example, it acts as an autotransformer. A single winding transformer. If you tap it half way it is technically the same as a 2:1 turns ratio (4:1 impedance) conventional transformer. Tap it one third of the way and its a 3:1 turns ratio (9:1 impedance). 73 … Ron On Mon, Jan 30, 2023 at 1:26 PM <timo.vandermerwe@...> wrote: Thx Ron, |
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