The Application of Negative Feedback to Microwave Bipolar Transistor Amplifiers

It is shown that RLC feedback between the base and collector of a microwave bipolar transistor enables one to design a single-stage unbalanced amplifier with a two-octave bandwidth (0.5 - 2.0 GHz). Over this bandwidth the measured terminal v.s.w.r.´s are within 2:1, the gain variation is ±1dB and a noise figure ¿4.6 dB has been achieved. The advantages of feedback are: (i) circuit design is simplified (ii) it is more economical than a balanced approach (iii) the gain of the amplifier can be varied by 3 dB by altering the collector current without degrading the terminal matches (iv) feedback reduces the effect of changes in transistor s-parameters (v) the amplifier is immune to parametric overload instabi1ities[1].