Yushan Li resumes & CV records
Resumes
Yushan Etal Li, 561034 Big Spring Dr, Allen, TX 75013
Yushan Li Phones & Addresses
1034 Big Spring Dr, Allen, TX 75013
Elk Grove, CA
Berthoud, CO
Sacramento, CA
Torrance, CA
Briarcliff Manor, NY
Boston, MA
Ossining, NY
Princeton, NJ
1337 Paramount Dr, Berthoud, CO 80513
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Yushan Etal Li
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Work
Position:
Professional/Technical
Education
Degree:
Associate degree or higher
Mentions for Yushan Etal Li
Publications & IP owners
Us Patents
Cmos Sub-Bandgap Reference With An Operating Supply Voltage Less Than The Bandgap
US Patent:
6617836, Sep 9, 2003
Filed:
May 8, 2002
Appl. No.:
10/142083
Inventors:
James T. Doyle - Nederland CO
Yushan Li - Longmont CO
Yushan Li - Longmont CO
Assignee:
National Semiconductor Corporation - Sunnyvale CA
International Classification:
G05F 316
US Classification:
323316, 323901, 327539, 327542
Abstract:
A circuit that outputs a stable reference voltage with an operating supply voltage less than the band gap potential and also less than a zero-bias threshold voltage. In one embodiment, the sub-band gap circuit includes an operational amplifier having an N-well input stage operating in the sub-threshold region, and a proportional to absolute temperature (PTA) current source having a forward-biased P-bulk. In another embodiment, the operational amplifier realizes sub-one volt operation by making use of back gating as the input stage, allowing full rail-to-rail input and output swings.
Method And System For Providing Power Management In A Radio Frequency Power Amplifier By Dynamically Adjusting Supply And Bias Conditions
US Patent:
6900697, May 31, 2005
Filed:
May 31, 2002
Appl. No.:
10/160281
Inventors:
James T. Doyle - Nederland CO, US
Dragan Maksimovic - Boulder CO, US
Yushan Li - Longmont CO, US
Dragan Maksimovic - Boulder CO, US
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
H03F003/04
US Classification:
330297, 330296
Abstract:
A method for providing power management in a radio frequency power amplifier is provided. An input voltage is received. A digital power supply signal is generated. From the input voltage, a regulated power supply signal is generated based on the digital power supply signal.
Method And System For Providing Power Management In A Radio Frequency Power Amplifier Using Adaptive Envelope Tracking
US Patent:
6914487, Jul 5, 2005
Filed:
Apr 17, 2003
Appl. No.:
10/417566
Inventors:
James T. Doyle - Nederland CO, US
Dragan Maksimovic - Boulder CO, US
Yushan Li - Longmont CO, US
Dragan Maksimovic - Boulder CO, US
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
H03F003/04
US Classification:
330297, 330129
Abstract:
A method for providing power management in a radio frequency power amplifier using adaptive envelope tracking is provided that includes receiving an input voltage. A power control signal is received. A feedback signal is received. An amplifier input signal is received. From the input voltage, a regulated power supply signal is generated based on the power control signal, the feedback signal, and the amplifier input signal.
System And Method For Providing A Highly Efficient Wide Bandwidth Power Supply For A Power Amplifier
US Patent:
7342387, Mar 11, 2008
Filed:
Feb 24, 2005
Appl. No.:
11/065255
Inventors:
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
G05F 1/40
G05F 1/56
G05F 1/56
US Classification:
323282, 323271
Abstract:
A system and a method are disclosed for providing a highly efficient wide bandwidth power supply for a power amplifier. A power supply control circuit of the invention comprises a wide bandwidth low drop out (LDO) circuit and a highly efficient switcher circuit. The switcher circuit comprises a switcher control circuit that receives an Icurrent signal from the low drop out (LDO) circuit and an Icurrent signal from the switcher circuit. The switcher control circuit uses the Ivalue and the Ivalue to control an amount of current that is provided by the switcher circuit. The Icurrent from the low drop out (LDO) circuit and the Icurrent from the switcher circuit are used to control a supply voltage Vthat is provided to a power amplifier.
Circuit And Method For Rf Power Amplifier Power Regulation And Modulation Envelope Tracking
US Patent:
7679433, Mar 16, 2010
Filed:
Feb 2, 2007
Appl. No.:
11/701747
Inventors:
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
H03F 3/38
US Classification:
330 10, 330297
Abstract:
A power amplifier receives an input signal and generates an amplified output signal. A switching converter generates a regulated voltage and performs power control for the power amplifier. A linear amplifier performs modulation envelope control for the power amplifier. The switching converter may be coupled in series with the linear amplifier, and this circuit may operate in one of multiple modes. For example, the linear amplifier may output a tracked voltage to the power amplifier in GSM/polar EDGE mode, and the switching converter may output the regulated voltage to the power amplifier in WCDMA/UMTS mode. The linear amplifier could also output the tracked voltage in both modes, and a selector could select the appropriate feedback voltage for the switcher. The switching converter could also provide the regulated voltage directly to the power amplifier, and the linear converter could adjust a bias of the power amplifier to provide envelope tracking.
System And Method For Suppressing Load Transients In Radio Frequency Power Amplifier Switching Power Supplies
US Patent:
7701690, Apr 20, 2010
Filed:
Jan 15, 2008
Appl. No.:
12/008843
Inventors:
Yushan Li - Longmont CO, US
Arthur J. Zirger - Boulder CO, US
Arthur J. Zirger - Boulder CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
H01H 47/00
US Classification:
361159, 455 631
Abstract:
A system and a method are disclosed for suppressing load transients in radio frequency power amplifier switching power supplies. A power supply control circuit is provided that includes a switcher circuit and a low drop out circuit. Load transients are suppressed by generating a preload control signal that activates an active current source either in the switcher circuit or in the low drop out circuit. The active current source counteracts a decrease in the switcher operating voltage when a load transient is present. Load transients are also suppressed by generating a step control signal that activates a transistor in a feedback resistor divider network in the switcher circuit to increase the switcher operating voltage during a load transient. The preload and step control signals are reset when the load transient has ended.
System And Method For Providing A Low Drop Out Circuit For A Wide Range Of Input Voltages
US Patent:
7723969, May 25, 2010
Filed:
Aug 15, 2007
Appl. No.:
11/893205
Inventors:
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
G05F 1/569
US Classification:
323276, 323273
Abstract:
A system and a method are disclosed for providing a low drop out circuit that can efficiently and correctly handle a wide range of input voltages. A power supply control circuit is provided for a low drop out circuit that comprises an operational amplifier that is coupled to a low drop out transistor. A switcher circuit provides one of a plurality of operating voltages to the low drop out transistor. The power supply control circuit provides a value of an operating voltage to the operational amplifier that enables the operational amplifier to operate the low drop out transistor in a manner that prevents the low drop out transistor from being out of control.
Feedback Loop Compensation For Buck/Boost Switching Converter
US Patent:
7821238, Oct 26, 2010
Filed:
Jun 9, 2008
Appl. No.:
12/157223
Inventors:
Yushan Li - Longmont CO, US
Assignee:
National Semiconductor Corporation - Santa Clara CA
International Classification:
G05F 1/613
US Classification:
323224, 323364
Abstract:
A system and a method are disclosed for providing an optimized feedback loop compensation for a buck/boost switching converter circuit. The buck/boost switching converter circuit may be operating in either a continuous conduction mode boost mode, or a continuous conduction mode buck mode, or a discontinuous conduction mode. A compensation circuit is provided that includes an error amplifier circuit that includes at least one compensation capacitor that provides an additional capacitance that adjusts a location of at least one dominant pole and at least one compensation zero of the buck/boost switching converter circuit to provide optimized feedback loop compensation.
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