PURPOSE: To obtain an excellent intermodulation characteristic over VHF∼UHF bands by inserting a negative feedback coupling means between a drain of a dual gate FET and the 1st gate and making the gate length of the 1st gate longer than the gate length of the 2nd gate.
CONSTITUTION: A feedback resistor R3 is selected to 300Ω and a dual gate FET Q1 where the 1st gatelength is 3μm and the 2nd gate length is 2μm is used to form a negative feedback amplifier with an AGC terminal. Further, the gate width and concentration of active layer of the FET Q1 are respectively 1,000μm and 1∼2×1017cm-3. The distortion characteristic of the negative feed back amplifier formed in this way has a signal level of ≥90dbμ over the entire gain control range as shown in I and a very excellent characteristic is obtained. The effect is obtained similarly also at the UHF band as well as the VHF band.
UEDA MASAYUKI
GODA KAZUHIDE
