Browse Prior Art Database

Sixteen-Input Funnel Utilizing Five-Level Differential Cascode Current Switch

IP.com Disclosure Number: IPCOM000047798D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Davis, JW: AUTHOR [+2]

Abstract

Cascode current switch (CCS) circuitry consists of reference level and differential types. Typically, one or two level CCS circuitry is reference level and utilizes dotting to obtain the desired function while 3 to 8 level CCS circuitry is of the differential type and does not generally utilize output dotting. It requires both input phases to be available and generates both output phases of the desired function if no output dotting is used. With present 5-volt semiconductor technology, 5-level CCS circuitry best utilizes the VBE drop across a transistor. This allows a maximum of 5 input variables for each Term (Boolean expression) used in a differential cascode current switch (DCCS) circuit (one current source).

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 2

Sixteen-Input Funnel Utilizing Five-Level Differential Cascode Current Switch

Cascode current switch (CCS) circuitry consists of reference level and differential types. Typically, one or two level CCS circuitry is reference level and utilizes dotting to obtain the desired function while 3 to 8 level CCS circuitry is of the differential type and does not generally utilize output dotting. It requires both input phases to be available and generates both output phases of the desired function if no output dotting is used. With present 5-volt semiconductor technology, 5-level CCS circuitry best utilizes the VBE drop across a transistor. This allows a maximum of 5 input variables for each Term (Boolean expression) used in a differential cascode current switch (DCCS) circuit (one current source). The number of terms may vary from 1 to 16 in each 5-level DCCS circuit, but Don't Care conditions frequently reduce the number of terms considerably. Fig. 1 shows an actual transistor connection in a 5-level DCCS circuit, while Fig. 2 is a shorthand version for representing the circuit function. The primary emphasis here is on the logical function of the circuit in Fig. 3 and the speed increase and circuit and power reduction that it offers. However, it is useful to understand the operation of the circuits in Figs. 1 and 2. The operation of the DCCS circuit shown in Fig. 1 (and Fig. 2) is as follows. Current flows through resistors R1 or R2 down through the differential tree to the ground point. The path it takes depends upon which "branches" of the tree are selected by the input variables, and the inputs to each transistor pair must be mutually exclusive so that only one transistor of each pair will conduct current if the balance of the tree is favorable. It may also be n...