International Business Machines Corporation

Floyd W Olsen

Edward J Tasillo

Matthew Francis Seward

Robert L Schaaf

Jerry K McMahon

An in-circuit ohmmeter is provided, including a pair of input terminals connectable to a resistance of an unknown value. A pair of current generators are connected electrically in series for generating an electrical current to be passed through the unknown resistance to develop a differential voltage across the input terminals, and a circuit is provided for determining the amount of the electrical current passed through the unknown resistance. A semiconductor switch switches the pair of current generators on and off. A current generator protection circuit comprising a plurality of diodes is connected across the input terminals. A differential amplifier circuit receives and amplifies the differential voltage so that a value of the unknown resistance may be calculated based on the differential voltage and the determined amount of electrical current passed through the resistance. An inverter circuit is disposed intermediate the input terminals and the differential amplifier circuit. The inverter circuit includes an inverter buffer circuit for electrically isolating the inverter circuit from the from input terminals. A pair of resistors and a pair of diodes electrically isolates each of the input terminals from the inverter circuit and the pair of current generators, respectively.

High voltage protected ohmmeter

A pulse width measurement circuit is provided, comprising (i) a comparator circuit for receiving a pulse, the time duration of which is to be measured, and for activating a pulse present signal in response to the received pulse; (ii) a counter for counting in response to the pulse present signal and for outputting a pulse count representing the duration of the received pulse; and (iii) a reset circuit for issuing a reset signal in response to a leading edge of the pulse present signal and for automatically resetting the counter to a base count in response to the leading edge of the pulse present signal. The comparator circuit is implemented in ECL circuitry and the counter is implemented in TTL circuitry. An ECL-to-TTL conversion circuit is disposed between the comparator circuit and the counter. The reset circuit includes a counter delay circuit for delaying the resetting of the counter for a predetermined time in response to the leading edge of the pulse present signal. A latch is clocked to store the contents of the counter in response to the trailing edge of the pulse present signal.

Pulse width measurement circuit

A method for detecting and locating constrictions in electrical conductors of predetermined normal cross-section. A test or reference resistance reading is made and stored pursuant to application of a test current, a stress current is applied, heating any constriction in the conductor, a resistance reading is taken immediately after the heating has taken place and the respective resistance readings are compared to determine the presence or absence of a constriction or weak spot. The disclosure also includes an exemplary circuit to implement the method. In an alternative embodiment, a second test current is applied immediately after the stress current.

Adiabatic conductor analyzer method and system

A high speed shunt regulator comprises a DC current source, a DC voltage reference/current shunt circuit, and first and second Schottky diodes connected in series with each other between the DC current source and the DC voltage reference/current shunt circuit. An output port for the load is connected between the first and second Schottky diodes. The Schottky diodes have little parasitic capacitance and virtually no reverse recovery. Consequently, the amount of current passing through the Schottky diodes can change in one nanosecond and the shunt regulator can accommodate high frequency fluctuations in the load while maintaining rated voltage. In other words, the Schottky diodes serve the function of 'isolating' the slower semiconductors of the DC current source and reference voltage/current shunt circuit from the load.

High speed shunt regulator

A signal to be scaled is supplied to three parallel amplifiers with gains of 0.1, 1, and 10, which each amplify the input simultaneously. The amplifiers are designed so that their output is limited to 1 volt regardless of the level of voltage at their input. This allows the lower magnitude portions of the signals to be amplified without amplifying the higher magnitude signals. The output of the amplifiers are summed together to provide the scaled signal.

Pseudo logarithmic analog step adder

Capacitance is measured using a system including a high voltage ramp monitor. A signal net is connected to ground by probes while a constant charging current is applied to the internal planes. A pure capacitive net will have a linear voltage rise proportional to capacitance, therefore its capacitance can be represented by ramp time. Leakage shorts will be detected by residual charge current measurements. The stimulus voltage is maintained for a fixed time after ramping to provide net to internal plane stress testing. Measured net capacitance is compared to nominal net capacitance for short/open detection.

Capacitance and leakage test method and apparatus

A circuit to function as an interface between larger test instrumentation having a high capacitance, including connecting leads, and a small, low current, monolithic chip device. This interface circuit has no internal control logic, is capable of transactions in both directions and is small itself, thereby fitting close to the monolithic chip device and reflecting a relatively low capacitance load to the chip. The interface circuit includes an input buffer amplifier connected to provide a driving voltage to drive the test instrumentation in response to a voltage from the small monolithic chip device, and a sensing resistor is connected with the input buffer amplifier so that their combined equivalent resistance value is substantially equal to the resistance reflected by the test instrumentation. An operational amplifier is connected to drive a small monolithic chip device in response to a voltage across the sensing resistor that is developed by the test instrumentation.

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Athens, PA, United States of America

Floyd W Olsen