Abstract: A transformerless solid state audio amplifier which exhibits the superior linearity and saturation characteristics of a triode vacuum tube amplifier, and which has an output impedance which nominally matches the impedance of a speaker is disclosed in which the gate of a low impedance transistor having triode-like current-voltage I-V characteristics is electrically coupled to an audio input source, the drain is electrically coupled to a supply voltage, a choke is connected in series between the drain and the supply voltage, and a speaker is coupled to the drain lead in parallel with the choke. Alternatively, a high impedance current source can be used instead of the choke.

Abstract: A YIG notch filter using full RF coupling loops and having a notch filter center frequency tunable as high as 18 GHz comprising a plurality of undoped YIG spheres of much smaller volume than used in the prior art and linearly arranged in a air gap. The spheres are suspended in cavities in a nonmagnetic block which are spaced much more closely than in the prior art. The 50 ohm stripline impedance inverters formed on a substrate and connecting the RF coupling loops of the spheres used in the prior art are eliminated. The quarter-wavelength impedance inverter function necessary to fabricate a notch filter is implemented by using the RF coupling loops themselves and measuring the distance from centerline to centerline of adjacent RF coupling loops. Twin insulated wires with up to one diameter separation for the RF coupling loops are preferred with the wires soldered together between the spheres.

Abstract: A controlled voltage yttrium iron garnet (YIG) resonator incorporates a clipping diode in order to maintain a constant output voltage. The clipping diode is connected either across an input or an output loop associated with the resonator. The resonator, as a result of its high Q characteristic, is insensitive to changes in capacitance of the clipping diode.