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Source Control Circuit for Schottky Barrier Diode Read Only Store

IP.com Disclosure Number: IPCOM000088051D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Cordero, W: AUTHOR

Abstract

This source control circuit has particular utility when employed in a read-only store (ROS), such as a 256 x 54 ROS. Its purpose is to control the current in the array such that there is negligible variation in potential between point A and VBB in the sense/output circuit when reading a "1" at the output. Also, by allowing the current to increase slightly with temperature, it will offset the performance loss due to the increase in resistance with temperature. Furthermore, the dynamic characteristics of this network greatly enhance the performance of the array. These goals are achieved by designing a source control circuit which controls the sense/array current in the following manner: a) There is negligible variation of Is with respect to VEE variations. b) There is a positive temperature coefficient.

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Source Control Circuit for Schottky Barrier Diode Read Only Store

This source control circuit has particular utility when employed in a read-only store (ROS), such as a 256 x 54 ROS. Its purpose is to control the current in the array such that there is negligible variation in potential between point A and VBB in the sense/output circuit when reading a "1" at the output. Also, by allowing the current to increase slightly with temperature, it will offset the performance loss due to the increase in resistance with temperature. Furthermore, the dynamic characteristics of this network greatly enhance the performance of the array. These goals are achieved by designing a source control circuit which controls the sense/array current in the following manner: a) There is negligible variation of Is with respect to VEE variations. b) There is a positive temperature coefficient. c)

Is is directly proportional to variations in VBB magnitude. d) Is is inversely proportional to variations in resistor magnitude. e) The presence of feedback causes the dynamic characteristics of Is to have an under-damped waveform.

The circuit functions as follows: R3, R4, R5, T1 and T2 form a differential amplifier whose inputs are VBB, and Alpha VEE, where Alpha is determined by R1, R2 and D1. Under nominal power supply conditions, inputs VBB and Alpha VEE are designed to be equal. As VEE is offset from nominal, a differential signal equal to AL Alpha Delta VEE AL is applied to the inputs, and is amplified by the gain of the differential amplifier (~R3/2R4), thereby causing node D to move in the same direction as the VEE supply. This signal is fed into the feedback amplifier, composed of R8, R9, R10, T5 and T6. The attenuation of the signal at node D is such that the potential between node C and VEE is held constant over the operating range of the VEE supply, thereby causing the current Is to remain constant with respect to VEE variations.

When VEE is held constant and VBB is allowed to vary, the signal Delta VBB is inverted,...