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Ultra high gain amplifier
This circuit uses a 2N3684 JFET and a 2N2686 JFET to form an ultra-high gain audio amplifier. Sometimes called the "JFET u (mu) amp", this circuit provides a very low power, high gain amplifying function. Since u (mu) of a JFET increases as drain current decreases, the lower the drain current is, the more gain you get. You do sacrifice input dynamic range with increasing gain, however.