Low Dropout Voltage Regulator for Highly Linear Radio Frequency Power Amplifiers
A radio frequency amplifier circuit has a signal input and a signal output. A primary amplifier is connected to the signal input and the signal output. A low dropout voltage regulator is connectible to an external power supply and to the primary amplifier, and generates a set voltage to bias the primary amplifier from a variable voltage provided by the external power supply. An equivalent capacitance circuit is connected to the primary amplifier and to the low dropout voltage regulator. The equivalent capacitance circuit defines a low dropout voltage regulator output capacitance in a nano-Farad to micro-Farad range absent any passive capacitor components corresponding thereto to maintain linearity of the primary amplifier.
1 - 26 . canceled
27 . A low dropout voltage regulator for a radio frequency amplifier circuit, comprising:
an operational amplifier connected to an external power source and including a reference input and an error input;
a reference voltage setting resistor connected to the reference input and to a current reference;
a feedback circuit connected to the error input of the operational amplifier, the feedback circuit defining a feedback factor and including a first feedback resistor and a second feedback resistor;
a first pass element connected to the external power source; and
a second pass element connected to the external power source and to the first pass element, an output port of the low dropout voltage regulator being defined by a junction of the first pass element and the second pass element, the output port being characterized by an equivalent capacitance value in a nano-Farad to micro-Farad range, and a predefined output voltage corresponding to the reference voltage setting resistor, the current reference, and the feedback factor being generated from the output port.
28 . The low dropout voltage regulator of claim 27 wherein an output impedance at the output port is within a predefined threshold from a baseband operating frequency range to a carrier frequency range.
29 . The low dropout voltage regulator of claim 27 wherein the output voltage transitions from off to on over a transient response rising edge corresponding to a pre-distortion to an amplifier circuit.
30 . The low dropout voltage regulator of claim 27 further comprising a current limiting resistor connected to the output port.