Constant output amplifier

Patent metadata

Field	Value
Publication number	US-9651960-B2
Application number	US-201514931256-A
Country	US
Kind code	B2
Filing date	Nov 3, 2015
Priority date	Jun 26, 2014
Publication date	May 16, 2017
Grant date	May 16, 2017

Abstract

Multi-stage amplifiers, such as linear regulators, provide a constant output voltage subject to load transients. The multi-stage amplifier includes a first amplification stage which activates or deactivates a first output stage in response to an input voltage at an input node. The first output stage sources a current at an output node of the multi-stage amplifier from a high potential, when activated. Furthermore, the multi-stage amplifier has a second amplification stage to activate or to deactivate a second output stage in response to the input voltage at the input node. The second output stage sinks a current at the output node of the multi-stage amplifier to a low potential, when activated. The first amplification stage and the second amplification stage activate the first output stage and the second output stage in a mutually exclusive manner.

First claim

What is claimed is:

1. A multi-stage amplifier comprising
a first amplification stage configured to activate or to deactivate a first output stage in response to an input voltage at an input node;
the first output stage configured to source a current at an output node of the multi-stage amplifier from a high potential, when activated;
a second amplification stage configured to activate or to deactivate a second output stage in response to the input voltage at the input node; and
the second output stage configured to sink a current at the output node of the multi-stage amplifier to a low potential, when activated; wherein the first amplification stage and the second amplification stage are configured to activate the first output stage and the second output stage in a mutually exclusive manner, wherein
the first output stage comprises
a first control transistor having a gate which is coupled to the first amplification stage, and being configured to vary a first control current through the first control transistor, subject to a voltage level at the gate of the first control transistor; and
a first output amplifier configured to source an amplified version of the first control current to the output node; and

the second output stage comprises
a second control transistor having a gate which is coupled to the second amplification stage, and being configured to vary a second control current through the second control transistor, subject to a voltage level at the gate of the second control transistor; and
a second output amplifier configured to sink an amplified version of the second control current at the output node.

2. The multi-stage amplifier of claim 1 , wherein
the first output stage comprises a first maintenance current source arranged in parallel to the first control transistor and configured to provide a first maintenance current to the first output amplifier; and/or
the second output stage comprises a second maintenance current source arranged in parallel to the second control transistor and configured to provide a second maintenance current to the second output amplifier.

3. The multi-stage amplifier of claim 1 , wherein
the first output amplifier comprises a first current mirror with a first diode transistor and a first output transistor;
the first diode transistor is arranged in series with the first control transistor such that the first diode transistor is traversed by the first control current;
a drain of the first output transistor is coupled to the output node;
the first output transistor is traversed by the amplified version of the first control current, which is sourced at the output node;
the second output amplifier comprises a second current mirror with a second diode transistor and a second output transistor;
the second diode transistor is arranged in series with the second control transistor such that the second diode transistor is traversed by the second control current;
a drain of the second output transistor is coupled to the output node; and
the second output transistor is traversed by the amplified version of the second control current, which is sunk at the output node.

4. The multi-stage amplifier of claim 3 , wherein
the first output transistor and the second output transistor are arranged in series;
the output node corresponds to a midpoint between the first output transistor and the second output transistor;
a source of the first output transistor is coupled to the high potential;
a source of the second output transistor is coupled to the low potential;
a source of the first diode transistor is coupled to the high potential;
a source of the first control transistor is coupled to the low potential;
a source of the second diode transistor is coupled to the low potential; and
a source of the second control transistor is coupled to the high potential.

5. The multi-stage amplifier of claim 1 , wherein
the first control transistor comprises an N-type metaloxide semiconductor, referred to as MOS, transistor;
the first output amplifier comprises P-type MOS transistors;
the second control transistor comprises a P-type MOS transistor; and
the second output amplifier comprises N-type MOS transistors.

6. The multi-stage amplifier of claim 1 , further comprising an auxiliary input transistor; wherein
a gate of the auxiliary input transistor is coupled to the input node;
a drain of the auxiliary input transistor is coupled to the output node; and
a source of the auxiliary input transistor is coupled to the low potential.

7. The multi-stage amplifier of claim 1 , wherein
the first amplification stage is configured to activate the first output stage, if the input voltage is at or below a pre-determined first threshold voltage;
the second amplification stage is configured to activate the second output stage, if the input voltage is at or above a pre-determined second threshold voltage; and
the second threshold voltage is equal to or greater than the first threshold voltage.

8. The multi-stage amplifier of claim 1 , further comprising
voltage sensing means configured to provide an indication of an output voltage at the output node; and
a differential amplification stage configured to provide the input voltage at the input node, based on a reference voltage and based on the indication of the output voltage at the output node.

9. A method for stabilizing an output voltage at an output node of a multi-stage amplifier, the method comprising
activating or deactivating a first output stage in response to an input voltage at an input node using a first amplification stage; wherein the input voltage at the input node is dependent on the output voltage at the output node;
activating or deactivating a second output stage in response to the input voltage at the input node using a second amplification stage; wherein the first amplification stage and the second amplification stage activate the first output stage and the second output stage in a mutually exclusive manner;
sourcing a current at the output node of the multi-stage amplifier from a high potential, by activating the first output stage, if the input voltage at the input node is indicative of an undervoltage situation at the output node; and
sinking a current at the output node of the multi-stage amplifier to a low potential, by activating the second output stage, if the input voltage at the input node is indicative of an overvoltage situation at the output node,
wherein
the first output stage comprises
a first control transistor having a gate which is coupled to the first amplification stage, and which varies a first control current through the first control transistor, subject to a voltage level at the gate of the first control transistor; and
a first output amplifier to source an amplified version of the first control current to the output node; and

the second output stage comprises
a second control transistor having a gate which is coupled to the second amplification stage, and which varies a second control current through the second control transistor, subject to a voltage level at the gate of the second control transistor; and
a second output amplifier to sink an amplified version of the second control current at the output node.

10. The method for stabilizing an output voltage at an output node of a multi-stage amplifier of claim 9 , wherein
the first output stage comprises a first maintenance current source arranged in parallel to the first control transistor and to provide a first maintenance current to the first output amplifier; and/or
the second output stage comprises a second maintenance current source arranged in parallel to the second control transistor and to provid

Assignees

• Dialog Semiconductor Uk Ltd

Inventors

• Kronmueller Frank
• Bhattad Ambreesh

Classifications

• G05F1/563 Primary

  including two stages of regulation at least one of which is output level responsive, e.g. coarse and fine regulation · CPC title

• G05F1/571

  with overvoltage detector · CPC title

• H03F2200/129

  there being a feedback over the complete amplifier · CPC title

• G05F1/562

  with a threshold detection shunting the control path of the final control device · CPC title

• G05F1/56

  using semiconductor devices in series with the load as final control devices (G05F1/461 takes precedence) · CPC title