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Tunnel Diode Switching Time Comparator

IP.com Disclosure Number: IPCOM000097864D
Original Publication Date: 1961-Aug-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Lieber, I: AUTHOR [+2]

Abstract

In the comparator, slope detection of the switching waveform is employed. The output of the diode Dt under test is applied across an RC differentiating circuit whose time constant is much shorter than the switching time t of the diode. Thus, the voltage appearing across the resistor is proportional to the switching speed of Dt. This voltage waveform is a very short pulse. It is amplified to a value sufficient to set a voltage sensitive latch whose output is used to turn on an indicator lamp.

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Tunnel Diode Switching Time Comparator

In the comparator, slope detection of the switching waveform is employed. The output of the diode Dt under test is applied across an RC differentiating circuit whose time constant is much shorter than the switching time t of the diode. Thus, the voltage appearing across the resistor is proportional to the switching speed of Dt. This voltage waveform is a very short pulse. It is amplified to a value sufficient to set a voltage sensitive latch whose output is used to turn on an indicator lamp.

To obtain an output from Dt that is independent of the input waveform, a very slow rising current input is used. The integrated output of a pulse generator furnishes this input which is applied, through a large resistor, across the diode.

The emitter follower, with its high input impedance, isolates the amplifier from the differentiator.

The amplifier output is fed to a tunnel diode emitter follower latch circuit. This circuit has an extremely well-defined switching threshold. That is, it discriminates between pulses whose amplitudes differ by as little as several millivolts. Tunnel diode D1 is biased at approximately .91/peak. When a pulse greater than
.11/peak is applied to the input, D1 switches to its high voltage state;, turning on transistor T3 and the indicator lamp. The latch is manually reset by S1.

In practice, a standard tunnel diode, whose switching time t is known to be the maximum acceptable, is inserted in the test socket....