High bandwidth, high PSRR, low dropout voltage regulator
View Patent ↗A voltage regulator may include one or more features for generating high PSRR. For example, source follower devices may be included in the voltage regulator for providing current sources for the output voltage nodes. The source followers may be sensitive to power supply noise at the gate terminal. Filters are included on the gate terminals to filter the power supply noise, thus reducing the noise at the gate terminals. As another example, the voltage regulator may employ current sources on the output voltage nodes which produce current inversely proportional to the current drawn by the load. In one embodiment, the voltage regulator may include a power control circuit used to provide overvoltage protection during power up. The power control circuit provides a voltage during power up, and ceases providing the voltage after a time interval so that the circuit may operate.
1. A circuit comprising:
a first transistor having a first terminal, a second terminal and a first gate terminal, wherein the first terminal is coupled to a power supply;
a resistor-capacitor (RC) filter coupled between the power supply and ground and coupled to the first gate terminal to reduce noise from the power supply at the first gate terminal;
a second transistor having a third terminal, a fourth terminal and a second gate terminal, wherein the third terminal is coupled to the second terminal to have the first transistor supply current to the second transistor, and wherein the fourth terminal is an output terminal to provide an output voltage; and
an operational amplifier circuit having its amplifier output coupled to the second gate terminal, wherein the fourth terminal is coupled to a feedback network of the operational amplifier circuit to regulate the output voltage.
2. The circuit as recited in claim 1 wherein an input of the operational amplifier circuit is coupled to an output of a bandgap generator, which sets a reference to regulate the output voltage.
3. A carrier medium comprising a database which is operated upon by a program executable on a computer system, the program operating on the database to perform a portion of a process to fabricate an integrated circuit including circuitry described by the database, the circuitry described in the database including:
a first transistor having a first terminal, a second terminal and a first gate terminal, wherein the first terminal is coupled to a power supply;
a resistor-capacitor (RC) filter coupled between the power supply and ground and coupled to the first gate terminal to reduce noise from the power supply at the first gate terminal;
a second transistor having a third terminal, a fourth terminal and a second gate terminal, wherein the third terminal is coupled to the second terminal to have the first transistor supply current to the second transistor, and wherein the fourth terminal is an output terminal to provide an output voltage; and
an operational amplifier circuit having its amplifier output coupled to the second gate terminal, wherein the fourth terminal is coupled to a feedback network of the operational amplifier circuit to regulate the output voltage.
4. The carrier medium as recited in claim 3 wherein an input of the operational amplifier circuit is coupled to an output of a bandgap generator, which sets a reference to regulate the output voltage.