
COLLECTING THE DATA IS ONLY THE FIRST STEP OF THE WISDOM, BUT SAHRING DATA IS THE FIRST STEP OF COMMUNITY.
source: http://cappels.org/dproj/edfet/edfet.html
The EDFET drives like a FET, but with the bias stability of bipolar. Amps of output current can be controlled by milliamps of input current. The current gain is a design choice dictated by bandwidth. Two of things you have to consider when adding a power output stage to an op-amp circuit are the frequency response and the cross-over distortion in that stage.
This is especially true with wide band amplifiers, where the unity gain crossover needs to be at several hundred kilohertz. The stage is driven much the same as a complimentary pair output stage, but with the current gain that comes with using FETs., and with feedback within the output stage that that extends the buffer's bandwidth and regulates the quiescent current. More predictable operation allows the designer to design a circuit lower overall power dissipation and better closed loop stability.