CMOS output buffer with negative feedback dynamic-drive control and dual P,N active-termination transmission gates
US6184730A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 3, 1999 |
| Grant date | Feb 6, 2001 |
| Priority date | — |
| Expiry date | Nov 3, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K19/00361
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An output buffer for a line driver uses transmission gates for active termination. A large p-channel driver is pulsed on during a low-to-high output transition, but this driver is turned off once the output voltage reaches a threshold. A feedback circuit includes a sensing inverter that has its input connected to the output node. The sensing inverter causes the gate of the p-channel driver to be driven high once the output swings past the threshold. A similar n-channel driver transistor is pulsed on during a low-going output transition but is disabled by a feedback circuit that senses the output voltage falling below a threshold. A pullup transmission gate is also connected between the output and the power supply, while a pulldown transmission gate is connected between the output and ground. Each transmission gate contains a p-channel and a n-channel transistor in parallel. The sizes of the p-channel and n-channel transistors in the transmission gate is sufficiently small to provide a resistance of 25 to 30 ohms. Both transistors in the pullup transmission gate are turned on when the output is driven high, while both transistors of the pulldown transmission gate are turned on when …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.