Tektronix, Inc.

John F Stoops

Daniel G Knierim

Steven K Sullivan

Marc A Gessford

Mark W Nightingale

Theodore G Nelson

John C Calvin

Michael P Khaw

Kelly F Cushing

Marie Ottum

A circuit includes a load; a first differential pair coupled to the load and responsive to input data; a second differential pair coupled to the load and responsive to the input data; a third differential pair coupled to the first differential pair and the second differential pair and responsive to a first control signal and a second control signal; a bias circuit configured to pull a node coupled to both the first differential pair and the second differential pair to a predetermined state; and a current source coupled to the third differential pair and the bias circuit.

Multifunction word recognizer element

A method and apparatus for an improved timer circuit and improved pulse width detection includes initiating a ramp timer and setting a timer latch output level substantially simultaneously in response to the occurrence of an input signal. The occurrence of the input signal also causes a counter to be enabled to count clock cycles. The ramp timer signal of the ramp timer is frozen (i.e., paused) by a timer control circuit, upon the occurrence of a first clock cycle following the enabling of the counter. The counter then counts a predetermined number of clock cycles after the ramp timer signal is frozen and, upon the occurrence of a last one of a predetermined number of clock cycles, generates a terminal count signal. Upon receiving the terminal count signal, the timer control circuit unfreezes ramp timer signal. The ramp timer runs until completion at which time the ramp timer generates an end of ramp control signal. The control signal is communicated to timer latch to reset timer latch output level.

Method and apparatus for an improved timer circuit and pulse width detection

A high impedance attenuator for use in a test and measurement instrument employs compensation to adjust the low frequency attenuation to match the high frequency attenuation exhibited by the attenuator, rather than attempting to adjust the high frequency attenuation exhibited by the attenuator. In an alternate embodiment of the invention, compensation to adjust low frequency attenuation is employed in a feedback loop and an opposite compensation is applied in a parallel attenuation stage to stabilize the input resistance. In yet another embodiment of the invention, compensation to adjust low frequency attenuation is employed by means of an R-C time constant of an additional R-C circuit in a feed forward loop. This additional time constant is matched to the R-C time constant of the input R-C network. The input resistance of the attenuator is not changed.

Apparatus and method for compensating a high impedance attenuator

A deskew fixture has a multilayer circuit board from which pairs of mirrored signal launch contact extend from both sides of the circuit board. One pair of contacts is coupled to electrical ground and the other pair is connected via equal length, electromagnetically coupled strip lines to a signal source. Probe holders are mounted on the circuit boards to support measurement probes with the probing contacts of the measurement probes coupled to the signal launch contacts. Additional pairs of signal launch contacts may be provided with one pair receiving a positive signal from the signal source and another pair receiving a negative signal via equal length, electromagnetically coupled strip lines from the signal source for deskewing differential measurement probes.

Deskew fixture

An oscilloscope comprises a trigger circuit for initiating display of the waveform of an input signal in response to a trigger event, at least one detection circuit responsive to the input signal for detecting occurrence of an anomalous event therein, and a counter for reporting the number of occurrences of the anomalous event that have been detected.

Oscilloscope with detection of anomalous events during blind intervals

An M-element waveform data sequence representative of an analog input signal during a period of interest is produced by first amplifying the input signal with a linear amplifier and periodically digitizing the amplifier output signal to produce a first data sequence having M+N-1 elements. The first N-1 elements of the first data sequence represent magnitudes of the amplifier output signal preceding the period of interest, and the remaining M elements of the first data sequence represent magnitudes of the amplifier output signal during the period of interest. The first data sequence is applied as input to a digital filter which produces an output second data sequence wherein each element of the second data sequence corresponds to an element of the first data sequence and is a linear combination of its corresponding first data sequence element and N-1 data preceding data elements of the first data sequence. The impulse response of the filter is adjusted to compensate for signal distortion caused by the amplifier. The desired M-element waveform data sequence is then obtained as the last M elements of the second data sequence.

Digital Correction of linear system distortion

A current signal limiter provides precise minimum and maximum current limiting. Both maximum and minimum current limits are easily programmable. The signal limiter operates at maximum frequency response without inversion of the input signal. Current signal limiting is achieved by an NPN transistor biased in a common base configuration with the base coupled to a reference voltage source and the collector providing the output current, a series diode coupled to the emitter of the transistor for receiving a trickle current which prevents the transistor from turning off as well as setting a minimum current limit, and a diode matrix for receiving two reference currents and an input current. The diode matrix steers the input and reference currents to the transistor or to the reference voltage source, depending on the magnitude of the input and reference currents. The minimum and maximum current limits are programmable by adjusting the values of the reference currents and the trickle current.

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Portland, OR, United States of America

John F Stoops