Probe apparatus and method for measuring high-frequency signals
AssigneeU.S. Philips Corporation
InventorsCornelis G. C. M. De Kort, Joris J. Vrehen
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Abstract
A probe apparatus includes a probe contact connected to a storage capacitance via a photoconductive switch. The photoconductive switch can be operated at high speed by means of a pulsed laser. The laser pulses (L) are synchronized with a moment in the operation cycle of the circuit at which moment the voltage at the point under test is to be measured. After a number of pulses and operation cycles the storage capacitance is charged to the voltage value (V) to be measured. Then, the capacitance does not form a load on the point under test and the voltage (V) can be determined accurately.
Claims15
A probe apparatus for measuring electrical signals in an electrical circuit comprising:
- at least one electrical contact for contacting a selected point of the electrical circuit, said electrical contact being coupled to a first terminal of a switch that is responsive to electromagnetic radiation, means for generating high frequency pulsed electromagnetic radiation in synchronism with the electric signal being measured and applying said pulsed electromagnetic radiation to said switch for switching the switch, and wherein a second terminal of said switch is connected to a capacitance for storage of an electrical quantity tapped from said elected circuit point and the apparatus parameters are chosen so that it requires two or more pulses of electromagnetic radiation to charge said capacitance to the voltage level of an electric signal being measured at said selected circuit point.
A method for sampling electrical signals in an electrical circuit with a repeated operation cycle, which method comprises contacting a point of the electrical circuit by a probe comprising a contact coupled to a storage capacitance via a photoconductive switch, closing the switch during a plurality of time intervals (L), each time interval being considerably sorter than one clock period for clocking the circuit, and synchronizing the intervals in which the switch is closed with the operation cycle of the circuit by applying laser pulses thereto in synchronism with said operation cycle.
A probe apparatus for measuring electric signals in an electric circuit comprising:
- an elongate optical fiber element having an elongate internal light conductive core and an outer coating tapered at one end,
- a transparent electric conductor arranged adjacent one end of the core which is located in the vicinity of said one tapered end;
- an electric contact point located at the end point of said one tapered end,
- a layer of photoconductive material sandwiched between the electric contact point and the transparent electric conductor, and
- a field effect transistor supported on said optical fiber element and electrically connected to said transparent electric conductor so as to function both a as a storage capacitor and as an input transistor of a pre-amplifier.
Dependencies are inferred from the claim text.