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Cascode Decoder

IP.com Disclosure Number: IPCOM000095149D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Gersbach, JE: AUTHOR [+2]

Abstract

Closely controlled input voltages, differentially connected to the inputs of a cascode decoder, provide high-speed operation at minimum power dissipation. Varying input voltages, required by the various levels of a cascode decoder, are developed by input powering switches connected along a voltage divider of dynamic resistance diodes. A differential connection of decoder and input powering switches permits operation at a constant power dissipation. This is because only one transistor per level is conducting.

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Cascode Decoder

Closely controlled input voltages, differentially connected to the inputs of a cascode decoder, provide high-speed operation at minimum power dissipation. Varying input voltages, required by the various levels of a cascode decoder, are developed by input powering switches connected along a voltage divider of dynamic resistance diodes. A differential connection of decoder and input powering switches permits operation at a constant power dissipation. This is because only one transistor per level is conducting.

The cascode decoder provides outputs 0... 7 at the top row of transistors. These transistors are made conductive by a negative pulse on their bases, developed as a result of a conductive path through three levels of cascode connected in a tree decoder. For example, the transistor for the 7 output requires that the 4, the 2, and the 1 input transistors below it each be conductive. The 3 output requires that the 4, the 2, and 1 transistors each be conductive.

The transistors in the decoder are controlled by input powering current switches (4) - (4), (2) - (2), and (1) - (1), one for each level. Since the decoder levels each provide a measurable voltage drop, their input requirements differ slightly from level to level.

To match the outputs of the input powering current switches to the needs of the decoder transistors, diodes 11, 12, and 13 are provided. The dynamic forward resistance of one diode can be selected to be comparable to the dynamic f...