Abstract: A semiconductor test instrument (12) provides an AC interrogating signal to an element under test, such as a single pin of an IC. Horizontal and vertical signals are developed and applied to a display (33) which produces an analog signature signal representative of the operating condition of the test element. The horizontal and vertical signals are converted to digital signals by an A-D converter (34) and stored in memory (39). An analog signature is also obtained from the same element as the test element but which is known to be good. The horizontal and vertical components of this signature are also converted into digital signals and stored in memory (42). The test and reference digital signals are then compared and those test digital signals which are different identified. The analog signatures corresponding to both the test and reference digital values are then reconstructed for display and superimposed, for viewing by an operator.

Abstract: The apparatus (10) includes a semiconductor tester (12) which in operation produces an analog signature signal relative to a circuit node of an electronic circuit, such as a pin connection of an integrated circuit. The analog signature signal is the result of horizontal and vertical signals which are also directed to an integrator/A-D converter (44) which produces therefrom a set of four digital signals representing said analog signature. These digital signals are then compared in a computer (50) against reference digital values for the same circuit node of the same electronic circuit which is known to be good. If the digital signals are not within a selected range relative to the reference digital values, the analog signature of the circuit node is displayed for inspection and evaluation by an operator.

Abstract: A signal source in the form of a 60 Hz voltage generator provides a 12 volt peak-to-peak signal to the primary winding of a transformer which has a secondary winding with upper and lower leads and a center tap lead. The voltage between the center tap lead and each of the upper and lower leads is 6 volts when the secondary winding is not loaded. A 5 ohm resistor is connected between the upper lead and ground, while the lower lead is connected to a first test lead. The other test lead is connected to ground. In operation, the test leads are placed across the junction of the semiconductor to be tested. The junction of the lower lead and the first test lead is connected to the input of a first amplifier, the output of which is applied to one of the horizontal deflection plates of an oscilloscope.

Abstract: A signal source in the form of a 60 Hertz voltage generator provides a 12 volt peak-to-peak signal to the primary winding of a transformer having a secondary winding which has an upper lead, a lower lead, a return lead which is between the upper and lower leads, and a tap lead between the lower lead and the return lead. The lower lead is connected through a variable resistance to the return lead. The movable arm of the variable resistance is connected to a first amplifier circuit, the output of which is applied to one of the horizontal deflection plates of an oscilloscope. The upper lead is connected through a 5 ohm resistor to ground and also to the input of a second amplifier circuit, the output of which is applied to one of the vertical deflection plates of the oscilloscope. The tap lead is connected to a first test lead, and the other test lead is connected to ground.

Abstract: The oscillator includes a high gain differential amplifier, the output of which alternately drives two sets of transistors which together provide the oscillator output signal. A first set of transistors operates during one-half cycle of the output while the other set is operating during the other half-cycle. A DC feedback path provides degenerative DC feedback to minimize the DC component of the output signal, while an AC feedback path, which includes a filter network which passes the circuit operating frequency at a 180.degree. phase shift relative to the phase of the output signal, provides regenerative AC feedback to maintain circuit oscillation.

Abstract: An extendible probe comprising an electrode and a body having two parts which cooperate to clamp the electrode in a desired position. The electrode comprises an elongated length of small diameter, electrically conducting, non-corrosive material which is electrically insulated except for the tip of one end, which is exposed and formed to a point. The two-part body has a longitudinal opening therethrough, which receives the electrode. The front part of the body, referred to as the tip, includes a tapered collett which extends away from the rear end thereof and which is compressed under pressure against the electrode, which passes therethrough. The rear part of the body, referred to as the barrel, overlays the collett and threadably engages the tip of the body. This arrangement permits controlled longitudinal movement of the barrel relative to the tip of the body.