Focus yoke, electromagnetically focused CRT display with the focus yoke, and negative feedback circuit with stray-capacitor-cancellation means used for the CRT display or the like

An electromagnetically focused CRT display including a focus yoke, said focus yoke comprising:

• cylindrical permanent magnet means which is disposed around a neck portion and is spaced from the circumference of the neck portion;
• core means for defining a toroidal space together with said cylindrical permanent magnet means for substantially surrounding said neck portion and for forming a magnetic path to guide magnetic lines of force generated by said cylindrical permanent magnet means;
• dynamic focus winding means disposed in said toroidal space;
• and
• eliminating winding means disposed externally of said toroidal space for eliminating an undesired magnetic field of an inverse polarity generated due to said cylindrical permanent magnet means.

A stray capacitor canceling negative feedback circuit comprising:

• amplifier means having non-inverted and inverted input terminals and an output terminal;
• winding means connected to the output terminal of said amplifier means;
• resistor means which is connected in series with said winding means for detecting a signal which is proportional to current flowing through said winding means;
• means for feeding back the signal which is detected by said resistor means to said inverted input terminal of said amplifier means;
• and
• at least a compensating capacitor means connected in series between said output terminal and said non-inverted input terminal of said amplifier means to cancel a portion of the signal fed back to said amplifier means caused by stray capacitance existing in parallel with said winding means.