Hartley oscillator requires no coupled inductors

摘要

EDN originally ran this Design Idea in its June 22,2006, issue. However, due to a number of schematic and textual errors, we have decided to run a corrected, up-to-date version here. We apologize for the errors and hope this version clears up any and all confusion. Examine a traditional Hartley oscillator circuit, and you'll note its trademark: a tapped inductor that determines the frequency of oscillation and provides oscillation-sustaining feedback. Although you can easily calculate the total inductance required for a given frequency, finding the coupling coefficient, k, poses technical difficulties and may require experimental optimization, also referred to as the "cut-and-try" method. This Design Idea presents an alternative equivalent circuit that allows you to model the circuit before building the prototype.