Improvement in the tetrode FET noise figure by neutralization and tuning

The noise figure of the tetrode FET is calculated, and it is shown that for frequencies near the cutoff frequency of the FET a considerable improvement in noise figure is possible by neutralizing the drain-gate capacitance C/SUB dg/ of the first half of the tetrode and by tuning the interstage network between the first and second half of the tetrode FET. To make this improvement possible, the tetrode FET must be provided with one extra lead connecting drain 1 + source 2 to the outside. The improvement is demonstrated for an FET cascode circuit.