Voltage regulator having MOS pull-off transistor for a bipolar pass transistor
US5617017A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 17, 1995 |
| Grant date | Apr 1, 1997 |
| Priority date | — |
| Expiry date | May 17, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05F3/20
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
An improved output driver is disclosed having a pull-off diode-connected transistor and a resistor for keeping a pass transistor off when no load current is desired. An MOS transistor is coupled in parallel with the pull-off diode. As the input voltage increases beyond a threshold level, the diode is no longer able to pull-off the pass transistor's base due to increasing leakage currents in the pass transistor and is thus unable to turn off the pass transistor. The MOS transistor turns on at this threshold voltage and pulls-off the pass transistor's base hard enough to keep the pass transistor off. In one embodiment, the MOS transistor is incorporated into an unadjusted field region of the diode-connected transistor without any additional masking or processing steps. Further, since it is formed in the field region of the diode, the inclusion of the MOS transistor requires no additional surface area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.