Harmonic-Amplifier Design

Two methods are presented for calculating the ideal performance of amplitude-variation-type harmonic amplifiers: (1), a slightly revised form of Terman´s analysis, which is convenient for quickly obtaining approximate results, and (2), a graphical analysis which, while somewhat less rapid, is exact. In a frequency-multiplier stage the actual performance may come short of the ideal because of degenerative effects due to grid-plate capacitance and cathode inductance. In many cases, with power tubes, these degenerative effects are so great as to render the stage impracticable. The degeneration due to grid-plate capacitance may be thought of as an output loading effect which is proportional to the mutual conductance and the grid-plate capacitance of the tube and inversely proportional to the total capacitance in the circuit between the grid and the cathode. Inductance in the cathode circuit common to both grid and plate circuits has a loading effect on both input and output circuits which is proportional to the mutual conductance of the tube, the common inductance, the internal capacitance between the cathode and the input or output electrode as the case may be, and to the second power of the frequency. Circuit arrangements for overcoming these degenerative effects are discussed in theory and application.