Composition of composite tube in analog circuit
It can be complex, because FET is a voltage controlled current device, the output current can not be directly under the input of a FET input; but the triode is current controlled device, can FET output current control triode output current, the amplification coefficient is higher.
Not because of the field effect transistor is complex, voltage controlled flow pipe, composite pipe composite pipe must have the corresponding current path, and you the first polar tube in DS there is no current path, and therefore cannot be combined
