> readeraz wrote:
> >Ringing choke circuit and blocking oscillator are different names of
> >oscillator.
> >Are they same meaning or they are different circuit in practice?
> >How to distinctly identify  them?

>   Both resemble variants of the Hartley oscillator, with the capacitor
> across the tapped inductor removed.

>   A blocking oscillator has the oscillation feedback path through a
> resistor and capacitor in parallel.  During the half-cycle where the
> transistor conducts, positive feedbck is through the capacitor.  Once the
> capacitor has become excessively charged to maintain enough feedback to
> keep the transistor saturated, this half-cycle ends.  This half-cycle is
> usually the shorter one.  During the other half-cycle, the transistor is
> off until the capacitor is discharged sufficiently by its paralleled
> resistor to allow current to flow through the base of the transistor.

>   In a ringing choke oscillator, the oscillation feedback (assuming a
> bipolar transistor) is through a resistor.  The "transistor-on" half cycle
> is usually the longer one.  That half-cycle ends when either the tapped
> inductor saturates or the transistor comes out of saturation.  The
> transistor-off half cycle's onset reinforces itself with the feedback
> winding's voltage changing in a direction to reduce the transistor's
> collector current.  In fact, once collector current starts decreasing, the
> transistor usually quickly slams off, and a high voltage pulse can occur.
>   If a ringing choke oscillator is not carefully designed, the transistor
> may be destroyed by breakdown from high voltage pulses resulting from
> suddenly interrupting current flowing through the inductor.
>   The transistor-off half cycle ends when the transistor's collector
> current has decreased to zero and has become steadily zero.  There may be
> a delay for stray capacitance charged by the high voltage pulse to
> discharge before the feedback winding produces voltage in the forward bias
> direction, but that is usually short.

>  - Don Klipstein (d...@misty.com)