Two-stage low-dropout frequency-compensating linear power supply systems and methods

A low-dropout (LDO) linear power supply system comprising:

• a pass-element configured to generate an output voltage at an output based on an input voltage;
• a compensation amplifier stage coupled to the output and configured to provide frequency compensation and to generate a stabilization voltage in response to a reference voltage and a feedback voltage representative of the output voltage, wherein the compensation amplifier stage comprises:
• a compensation operational amplifier (OP-AMP) configured to generate the stabilization voltage at an output of the compensation OP-AMP based on the reference voltage at a first input of the compensation OP-AMP and the feedback voltage at a second input of the compensation OP-AMP:
• a resistive-capacitive feed-forward network coupled between the LDO output and the second input of the compensation OP-AMP and configured to generate a feed-forward output voltage that is a fraction of the output voltage at the LDO output, wherein the resistive-capacitive feed-forward network comprises a first resistive voltage-divider and a second resistive voltage-divider, the first resistive voltage divider providing a first divided voltage via a first resistor and a first capacitor, the second resistive voltage divider providing a second divided voltage via a second resistor, the first divided voltage and the second divided voltage configured to be combined to generate the feed-forward output voltage;
• and
• a resistive-capacitive feedback network coupled between the second input and the output of the compensation OP-AMP and configured to feedback the stabilization voltage to the second input, wherein the feedback voltage generated at the second input of the compensation OP-AMP is generated based on a portion of the stabilization voltage and the feed-forward output voltage;
• and
• a gain amplifier stage interconnecting the compensation amplifier stage and the pass-element and configured to generate a control voltage based on the stabilization voltage and which has a frequency response that is approximately equal to a frequency response of the stabilization voltage, the control voltage being provided to the pass-element with direct current (DC) gain scaling of the stabilization voltage to generate the output voltage proportional to the input voltage;
• and
• a second capacitor and an associated equivalent series resistance (ESR) coupled to the output to provide output filtering of the output voltage.

An integrated circuit (IC) chip comprising a low-dropout (LDO) linear power supply system, the LDO linear power supply system comprising:

• a pass-element configured to generate an output voltage at an output based on an input voltage;
• a compensation amplifier stage coupled to the LDO output and configured to provide frequency compensation and to generate a stabilization voltage in response to a reference voltage and a feedback voltage representative of the output voltage, wherein the compensation amplifier stage comprises:
• a compensation operational amplifier (OP-AMP) configured to generate the stabilization voltage at an output of the compensation OP-AMP based on the reference voltage at a first input of the compensation OP-AMP and the feedback voltage at a second input of the compensation OP-AMP:
• a resistive-capacitive feed-forward network coupled between the LDO output and the second input of the compensation OP-AMP and configured to generate a feed-forward output voltage that is a fraction of the output voltage at the LDO output, wherein the resistive-capacitive feed-forward network comprises a first resistive voltage-divider and a second resistive voltage-divider, the first resistive voltage divider providing a first divided voltage via a first resistor and a first capacitor, the second resistive voltage divider providing a second divided voltage via a second resistor, the first divided voltage and the second divided voltage configured to be combined to generate the feed-forward output voltage;
• and
• a resistive-capacitive feedback network coupled between the second input and the output of the compensation OP-AMP and configured to feedback the stabilization voltage to the second input, wherein the feedback voltage generated at the second input of the OP-AMP is generated based on a portion of the stabilization voltage and the feed-forward output voltage;
• and
• a gain amplifier stage interconnecting the compensation amplifier stage and the pass-element and comprising a gain OP-AMP configured to receive the stabilization voltage at a first input of the gain OP-AMP and to generate a control voltage at an output of the gain OP-AMP, the control voltage being provided to control the pass-element at a control input, the gain amplifier stage being configured to provide direct current (DC) gain scaling of the control voltage relative to the stabilization voltage to control the pass-element to generate the output voltage proportional to the input voltage;
• and
• terminals configured to receive a second capacitor and an associated equivalent series resistance (ESR) coupled to the output external to the IC to provide output filtering of the output voltage.

A low-dropout (LDO) linear power supply system comprising:

• a pass-element configured to generate an output voltage at an output based on an input voltage;
• a compensation amplifier stage coupled to the LDO output and configured to provide frequency compensation and to generate a stabilization voltage in response to a reference voltage and a feedback voltage representative of the output voltage, wherein the compensation amplifier stage comprises:
• a compensation operational amplifier (OP-AMP) configured to generate the stabilization voltage at an output of the compensation OP-AMP based on the reference voltage at an inverting input of the compensation OP-AMP and the feedback voltage at the inverting input of the compensation OP-AMP:
• a resistive-capacitive feed-forward network coupled between the LDO output and the inverting input of the compensation OP-AMP and configured to generate a feed-forward output voltage that is a fraction of the output voltage at the LDO output, wherein the resistive-capacitive feed-forward network comprises a resistive voltage-divider, the resistive voltage divider providing a divided voltage via a first resistor, a second resistor and a first capacitor to generate the feed-forward output voltage;
• and
• a resistive-capacitive feedback network coupled between the inverting input and the output of the compensation OP-AMP and configured to feed back the stabilization voltage to the inverting input, wherein the feedback voltage generated at the inverting input of the compensation OP-AMP is generated based on a portion of the stabilization voltage, the feed-forward output voltage and the reference voltage, wherein the reference voltage and the output voltage are directly interconnected by the resistive voltage divider;
• and
• an a gain amplifier stage interconnecting the compensation amplifier stage and the pass-element and configured to generate a control voltage based on the stabilization voltage and which has a frequency response that is approximately equal to a frequency response of the stabilization voltage, the control voltage being provided to the pass-element with direct current (DC) gain scaling of the stabilization voltage to generate the output voltage proportional to the input voltage within a given range of the input voltage.