Creating additional phase margin in the open loop gain of a negative feedback amplifier system
First Claim
1. A negative feedback amplifier system comprising:
- a first current control element having a first terminal connected to a supply voltage, a control terminal, and a second terminal connected to an output terminal;
an output stabilization circuit including;
a second current control element having a first terminal connected to the voltage supply, a control terminal, and a second terminal, and a first resistor coupled between the second terminal of the second current control element and the output terminal; and
an amplifier having at least one input terminal coupled to the second terminal of the second current control element, the amplifier also having an output terminal connected to the control terminals of the first and second current control elements.
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Accused Products
Abstract
A low-dropout voltage (LDO) regulator that creates a zero in the open loop gain using a relatively small-sized current control element to divert part of the supplied load current through a “zero” resistor before adding it to the output load. The main part of the output load is passed through a relatively large second current control element, and both the current control elements are controlled by a control signal generated by an error amplifier (e.g., an op-amp). The voltage signal developed across the “zero” resistor mimics the magnitude and phase of a zero in the loop. This voltage signal is added to the loop gain by, for instance, using a bypass capacitor, and the resulting feedback signal is supplied to the error amplifier, which generates a control signal by comparing the feedback signal with a stable reference voltage.
40 Citations
20 Claims
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1. A negative feedback amplifier system comprising:
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a first current control element having a first terminal connected to a supply voltage, a control terminal, and a second terminal connected to an output terminal;
an output stabilization circuit including;
a second current control element having a first terminal connected to the voltage supply, a control terminal, and a second terminal, and a first resistor coupled between the second terminal of the second current control element and the output terminal; and
an amplifier having at least one input terminal coupled to the second terminal of the second current control element, the amplifier also having an output terminal connected to the control terminals of the first and second current control elements. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A low dropout voltage (LDO) regulator having an input terminal and an output terminal, the LDO regulator comprising:
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a first current control element having a first terminal connected to the input terminal, a control terminal, and a second terminal connected to the output terminal;
an output stabilization circuit including;
a second current control element having a first terminal connected to the input terminal, a control terminal, and a second terminal, and a first resistor coupled between the second terminal of the second current control element and the output terminal; and
an error amplifier having a first input terminal coupled to the output stabilization circuit, a second input terminal connected to a reference voltage source, and an output terminal connected to the control terminals of the first and second current control elements. - View Dependent Claims (9, 10, 11, 12)
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13. A portable device comprising:
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a power source for generating an input signal;
a load circuit; and
a voltage regulator having an input terminal connected to the power source and an output terminal connected to the load circuit, wherein the voltage regulator comprises;
a first current control element having a first terminal connected to the input terminal, a control terminal, and a second terminal connected to the output terminal;
an output stabilization circuit including;
a second current control element having a first terminal connected to the input terminal, a control terminal, and a second terminal, and a first resistor coupled between the second terminal of the second current control element and the output terminal;
an error amplifier having a first input terminal coupled to the output stabilization circuit, a second input terminal connected to a reference voltage source, and an output terminal connected to the control terminals of the first and second current control elements. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification