The author of the original EW article mentioned using a plain gate-source connected JFET, which is selected to produce 1mA current. They have poor Vce(max), so their supply voltage is reduced using a simple Zener diode regulator built using R3, ZD1 and C3. The input devices used (2SA970) are low-noise, high gain PNP devices. Overall Negative Feedback is used to set the gain to 27dB and to reduce the distortion. Since their transconductance is low, the rest of the design is geared towards producing maximum open-loop gain. It uses inexpensive HexFet™ Power MOSFETs as output devices. This circuit is from David White's article in Electronics World (August 2001).
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