Compact low dropout voltage regulator using enhancement and depletion mode MOS transistors
First Claim
1. A dual function reference voltage generator and amplifier circuit for generating an output signal that is responsive to differences between an input signal and reference voltage comprising:
- a power source that includes a high voltage node and a low voltage node;
a voltage reference MOS transistor connected between said high voltage node and said low voltage node, said voltage reference MOS transistor having a gate connected to an input terminal to receive said input signal; and
a current source means for providing a generally fixed current to said voltage reference MOS transistor, said current source means including a first depletion mode MOS transistor connected in series between said high voltage node and said voltage reference MOS transistor.
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Accused Products
Abstract
A low dropout (LDO) voltage regulator for generating a well-regulated voltage which is stable with variations in load resistance and in supply voltage includes a non-complex reference voltage generator. In the preferred embodiment, the reference voltage generator is configured to function as an amplifier as well as a reference voltage generator. In one embodiment, a single gain stage LDO voltage regulator utilizes the single function reference voltage generator which is compared to a feedback voltage that is proportional to an output voltage. The feedback voltage and the reference voltage control two currents which are used to generate a control signal to a pass transistor. Depending on the supply voltage, the pass transistor either increases or decreases the current to an output terminal to raise or lower the output voltage until the output voltage equals the regulated voltage. In another embodiment, a two gain stage LDO voltage regulator utilizes the dual function reference voltage generator. The two gain stage LDO voltage regulator compares a gained signal instead of the reference voltage with the feedback voltage to generate the control signal to the pass transistor.
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Citations
18 Claims
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1. A dual function reference voltage generator and amplifier circuit for generating an output signal that is responsive to differences between an input signal and reference voltage comprising:
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a power source that includes a high voltage node and a low voltage node; a voltage reference MOS transistor connected between said high voltage node and said low voltage node, said voltage reference MOS transistor having a gate connected to an input terminal to receive said input signal; and a current source means for providing a generally fixed current to said voltage reference MOS transistor, said current source means including a first depletion mode MOS transistor connected in series between said high voltage node and said voltage reference MOS transistor. - View Dependent Claims (2, 3, 4)
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5. A voltage regulator having an output terminal comprising:
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a power source that includes a high voltage rail and a low voltage rail; a dual function reference voltage generator and amplifier circuit that generates a first gain signal which is responsive to a difference between a reference voltage and a feedback voltage, said dual function reference voltage and amplifier circuit including a series connection of a first depletion mode MOS transistor and a first enhancement mode MOS transistor between said high voltage rail and said low voltage rail, said first depletion mode MOS transistor having interconnected gate and source electrodes, said first enhancement mode MOS transistor having a gate connected to receive said feedback voltage; a pass transistor having a first electrode connected to said high voltage rail, a second electrode connected to said output terminal, and a control electrode which is responsive to said first gain signal; and a feedback path connected to said dual function reference voltage generator and amplifier circuit to provide said feedback voltage, said feedback voltage having a magnitude that is responsive to an output voltage at said output terminal. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. An efficient voltage regulator having an output terminal comprising:
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a power source that includes a high voltage rail and a low voltage rail; a reference voltage generating circuit including a series connection of a first depletion MOS transistor and a first enhancement mode MOS transistor between said high voltage rail and said low voltage rail, said first depletion mode MOS transistor having a gate connected to its source, said first enhancement mode MOS transistor having a gate connected to its drain, said reference voltage generator circuit having an output of a reference voltage, said reference voltage further including a second depletion mode MOS transistor and a second enhancement mode MOS transistor, said second depletion mode MOS transistor connected in series between said high voltage rail and said first depletion mode MOS transistor such that gates of both depletion mode MOS transistors are coupled, said second enhancement mode MOS transistor connected in series between said first depletion mode MOS transistor and said first enhancement mode MOS transistor such that gates of both enhancement mode MOS transistors are coupled; an error amplifier means, connected to said reference voltage generator circuit, for generating an error signal that represents a difference between a reference current that is responsive to said reference voltage and a feedback current that is responsive to an output voltage at said output terminal; a pass transistor having a first electrode connected to said high voltage rail, a second electrode connected to said output terminal, and a control electrode which is responsive to said error signal, said output voltage thereby being responsive to said error signal; and a feedback path connected to said error amplifier means to provide a feedback voltage, said feedback voltage being responsive to said output voltage. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification