Apparatus and method for generating a step voltage waveform

An apparatus for generating a step voltage waveform, comprising:

• first means for receiving a switching signal;
• second means, responsive to said switching signal, for producing an intermediate signal switchable between at least a first voltage and a second voltage, said second means including a first path comprising a first plurality of switching devices in series coupled to a second path comprising a second plurality of switching devices in series;
• third means, responsive to the switching of the intermediate signal from the said first voltage to the said second voltage, for providing a fast step voltage waveform as an output signal said third means including a third path of a third plurality of switching devices in series;
• and
• fourth means for coupling said second path and said third path and for inhibiting current flow to said third path until said second means has produced an intermediate signal of said second voltage, said fourth means having a high, impedance for high frequency signals.

An apparatus for generating a driving signal to a step signal output generator, comprising:

• first means for receiving a trigger signal;
• second means for producing a bias current;
• a first current path, coupled to said first means, and responsive to said trigger signal and a first portion of said bias current, producing a preliminary output of said trigger signal and said first portion of said bias content, said first current path including a plurality of switching devices connected in series;
• a second current path, coupled to said first current path, and responsive to a second portion of said bias current and said preliminary output to produce, with said first current path, a driving signal, said second current path including a second plurality of switching devices connected in series;
• and
• an element coupled between said second path and said step signal output generator, said element having a high impedance for high frequency signals and inhibiting current flow to said step signal output generator until said first plurality and said second plurality of switching devices have all switched states to produce said driving signal.

In a time domain reflectometer comprising a step signal output generator, a means for receiving a trigger signal, and a means for producing a driving signal to said step signal output generator in response to said trigger signal, the improvement comprising:

• said means for producing a driving signal including,
• first means for producing a bias current;
• a first current path coupled to said means for receiving a trigger signal, and responsive to said trigger signal and a first portion of said bias current, producing a preliminary output of said trigger signal and said first portion of said bias current, said first current path including a plurality of switching devices connected in series;
• a second current path, coupled to said first current path, and responsive to a second portion of said bias current and said preliminary output to produce a driving signal, said second current path including a second plurality of switching devices connected in series;
• and
• an element coupled between said second path and said step signal output generator, said element having a high impedance for high frequency signals and inhibiting a driving signal from flowing to said step signal output generator until all of said first plurality and said second plurality of switches have switched state.