Bidirectional Shift Register Using Homogeneous P-Type Transistors
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Solution Overview
Problem
The existing CMOS bidirectional shift registers require two sets of different photo masks for manufacturing, increasing the cost due to the use of CMOS elements with different types of transistors.
Innovation Solution
A bidirectional shift register design utilizing transistors of the same type, specifically P-type MOS transistors, which simplifies the manufacturing process by reducing the need for multiple photo masks, allowing for the use of a single set of masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CMOS elements with different types of transistors (N-type and P-type) are used to achieve bidirectional control functionality, then the bidirectional shift register can switch directions for scanning, but two sets of different photo masks are needed for manufacturing, increasing manufacturing cost
Solution Approach 1:
The patent applies homogeneity by using only P-type MOS transistors throughout the entire bidirectional shift register circuit, including in the SR latch circuits and control circuits. This eliminates the need for both N-type and P-type transistors, allowing manufacturing with a single photo mask set while maintaining full bidirectional scanning functionality through clever circuit design and transistor configuration
2Adaptability or versatility
If two sets of different photo masks are used to manufacture CMOS elements with different transistor types, then bidirectional control functionality is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses exclusively P-type MOS transistors in all circuit blocks, creating a homogeneous transistor type architecture. This simplifies the manufacturing process to require only one set of photo masks, reducing device complexity in the manufacturing process while preserving the bidirectional control functionality through the designed circuit operations
Solution Approach 2:
The P-type MOS transistors are designed to perform multiple functions: they serve as storage elements in the SR latch circuits, as control elements in the bidirectional control circuits, and as switching elements. This multi-functionality of a single transistor type eliminates the need for different transistor types and reduces the number of photo mask sets required
Data Source
AI summary
A bidirectional shift register includes a former stage multiplexer, a latter stage multiplexer, a former stage full-swing shift register, and a latter stage full-swing shift register, all of which have a plurality of registers all of the same type. The former and the latter stage multiplexers output signals according to a forward clock, a backward clock, a forward control signal, and a backward control signal. The former and the latter stage full-swing shift register store the signals output from the former and the latter stage full-swing shift registers respectively.