Patent ID: 7227392

Claim:
A frequency multiplier comprising: a multiplier core for outputting a single-phase output signal containing a frequency component having a first frequency that is an even multiple of the frequency of an input signal; a differential amplifier including a first input terminal receiving the output signal from said multiplier core, and a second input terminal grounded through a capacitor, said differential amplifier differentially amplifying the output signal from said multiplier core and a signal at said second input terminal and providing a differential output; and a series LC circuit, wherein said differential amplifier includes first and second transistors, each of said first and second transistors having a first current terminal, a second current terminal, and a control terminal, said second current terminals of said first and second transistors are connected to each other, said control terminal of said first transistor is said first input terminal of said differential input amplifier, said control terminal of said second transistor is said second input terminal of said differential input amplifier, and said multiplier core has an output terminal connected through said series LC circuit to said second current terminals of said first and second transistors of said differential amplifier.