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<\/p>\nWhy power JFET\u2019s you ask? Don\u2019t we have enough transistors already? We do have lots of choices in devices, but a power JFET brings some particular advantages to the table that we don\u2019t get elsewhere.<\/p>\n
First off, for comparable devices at a given bias current, we see that the power JFET has much less distortion. The original F3 circuit was designed with a MOSFET, and comparing \u201capples to apples\u201d, the power JFET operated with one-fifth the distortion of the MOSFET.<\/p>\n
That\u2019s only the beginning. The JFET has much less distortion operated as if it were a MOSFET, but it\u2019s not a MOSFET, and it has characteristics which allow for even better performance by working the load line of the amplifier, much as found in tube design. To do this, I developed the Modulated Cascode \u2122 which allows arbitrary ratios of voltage and current (the load line) independent of the actual load value and reactance.<\/p>\n
In recent years, advances have been made in vertical JFET design which makes them more competitive in switching applications, and as a result power JFETs have been re-introduced after a thirty-year absence. Earlier this year I published the \u201cZen Variations #8 \u2013 the Power JFET Amplifier\u201d and now First Watt is introducing the model F3. (At introduction, the world\u2019s only commercially available amplifier using power JFETs).<\/p>\n
This is what the simplified schematic of this amplifier looks like:<\/p>\n
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It’s a little hard to believe that such a simple little amplifier and achieve distortion as low as 0.003% distortion at 1 watt into an 8 ohm load.<\/p>\n","protected":false},"excerpt":{"rendered":"