Abstract: An apparatus for displaying analog signatures of an electronic device is attached to the electronic device and periodically subjects the electronic device to one, two, three or four selected test conditions. The responses of the electronic device to each of the test conditions are received as a pair of response signals, which constitute an analog signature of the electronic device. The two signals in each signature are respectively used to drive horizontal and vertical deflections of a CRT, which causes the signatures corresponding to each of the selected test conditions to be displayed simultaneously. If desired, the apparatus can be attached to a second electronic device, the selected test conditions alternately applied to the two devices, and the corresponding signatures alternately displayed on the CRT. This allows comparisons of the two electronic devices to be readily made.

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.