Timebase generator with improved linearity and recovery time

In a circuit for producing a repetitive time base sweep, said circuit including a timing capacitor, means for changing the charge on said capacitor for providing a time base sweep signal starting from an initial baseline value, and means for reversing said change in charge on said capacitor at the end of the time base sweep to provide a retrace period concluding with return to said initial baseline value, said last mentioned means including a current switch having a first switching position during the time base sweep and a second switching position for providing an additional current path to said capacitor substantially at the end of the time base sweep and until the beginning of the next time base sweep, the improvement comprising:

• means for supplying a first value of current through said current switch during said retrace period, and a lower value of current through said current switch thereafter so that said lower value of current is present when said current switch returns to said first switching position for initiation of the next time base sweep.

A circuit for producing a time base sweep, said circuit including a timing capacitor and means for providing a current to said capacitor for generating a time base sweep,

• wherein said means for providing a current comprises a semiconductor device having an inherent capacitance that reduces the current that would otherwise be provided to said timing capacitor, and
• means for providing a compensating current to said timing capacitor to neutralize the current lost to the inherent capacitance of said semiconductor device.

The method of operating a time base sweep circuit in response to a gating signal, wherein said circuit includes a timing capacitor, means for providing a time base sweep beginning from an initial value, and means for providing a second current path to said capacitor comprising the steps of:

• coupling said additional current path to said capacitor for providing a retrace period back to said initial value in response to a given portion of said gating signal,
• susequently decoupling said additional current path from said capacitor for the subsequent initiation of a following time base sweep in response to another portion of said gating signal, and
• limiting the current in said additional current path to a level lower than during retrace substantially at the end of each said retrace period at starting substantially at the end of each said retrace period and continuing at least until said additional current path is subsequently decoupled for the initiation of the following time base sweep.