Voltage stabilizer with a very low voltage drop designed to withstand high voltage transients

• US 5,036,269 A
• Filed: 12/28/1989
• Issued: 07/30/1991
• Est. Priority Date: 12/28/1988
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV)
• Original Assignee: SGS-Thomson Microelectronics, S.R.L. (STMicroelectronics NV)
• Inventors: Murari, Bruno, Morelli, Marco, Maggioni, Giampietro
• Primary Examiner(s): Wong, Peter S.
• Application Number:
  US07/458,373
• Time in Patent Office: 579 Days
• Field of Search: 323/266, 323/268, 323/270, 323/273, 323/274, 323/275, 323/276, 323/280, 323/281, 323/299, 323/303, 361/18
• US Class Current: 323/266
• CPC Class Codes: G05F 1/571 with overvoltage detector

Abstract

A voltage stabilizer with a very low voltage drop includes a series voltage regulator circuit having a first PNP transistor connected to an input terminal of the stabilizer via a second PNP transistor and being connected to ground via a capacitor. The stabilizer has biasing and switching circuits disposed between the input terminal thereof, a base terminal of the second transistor and ground.

Claims

1. A monolithically integratable voltage stabilizer comprising:

a first bipolar transistor of a first type of conductivity having an emitter terminal which is connected to ground via a capacitor, and having a collector terminal which forms an output terminal of the stabilizer, and having a base terminal;

a differential amplifier having an output terminal which is connected to said base terminal of said first bipolar transistor and having a first input terminal which is connected to a voltage divider connected between said output terminal of the stabilizer and ground, and having a second input terminal which is connected to a first voltage reference;

a second bipolar transistor of said first type of conductivity having an emitter terminal which forms an input terminal of the stabilizer, and having a collector terminal which is connected to said emitter terminal of said first transistor and having a base terminal which is connected to a biasing and switching circuit means disposed between said base terminal of said second transistor and ground and said input terminal of the stabilizer.

2. A voltage stabilizer as claimed in claim 1, wherein said biasing and switching circuit means comprises a switch disposed between said base terminal of said second transistor and ground.

3. A voltage stabilizer as claimed in claim 2, wherein said switch comprises a transistor included in a current mirror circuit having an input branch connected both to a second voltage reference and to said input terminal of the stabilizer and having an output branch connected to said base terminal of said second transistor.

4. A voltage stabilizer as claimed in claim 2, wherein said biasing and switching circuit means comprises a threshold comparator circuit means for opening said switch when a potential at said input terminal of the stabilizer is lower than a first predetermined value and when it is greater than a second predetermined value.

5. A voltage stabilizer as claimed in claim 1, wherein said first transistor comprises a PNP transistor with an isolated vertical collector and wherein a second transistor comprises a lateral PNP transistor.