Apparatus and methods for power amplifier envelope tracking systems with automatic control of a slew rate and a mode of an error amplifier of the envelope tracking system. The envelope tracker can include a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a control circuit that controls the slew rate of the error amplifier based on the detected signal bandwidth.

A switching driver circuit may have an output stage having an output switch connected between a switching voltage node and an output node. A switch network may control a switching voltage at the switching voltage node so that in one mode the switching voltage node is coupled to a positive voltage and in another mode the switching voltage node is coupled to ground voltage via a first switching path of the switch network. The circuit may also include an n-well switching block operable to, when the first switching voltage node is coupled to a positive voltage, connect the n-well of the first output switch to the switching voltage node, and, when the first switching voltage node is coupled to the ground voltage, connect the n-well of the first output switch to a first ground which is separate to the first switching voltage node and independent of the first switching path.

Provided is a comparison circuit to which a negative voltage to be compared can be input directly. The comparison circuit includes a first input terminal, a second input terminal, a first output terminal, and a differential pair. The comparison circuit compares a negative voltage and a negative reference voltage and outputs a first output voltage from the first output terminal in response to the comparison result. The negative voltage is input to the first input terminal. A positive reference voltage is input to the second input terminal. The positive reference voltage is determined so that comparison is performed. The differential pair includes a first n-channel transistor and a second n-channel transistor each having a gate and a backgate. The first input terminal is electrically connected to the backgate of the first n-channel transistor. The second input terminal is electrically connected to the gate of the second n-channel transistor.

Provided is a comparison circuit to which a negative voltage to be compared can be input directly. The comparison circuit includes a first input terminal, a second input terminal, a first output terminal, and a differential pair. The comparison circuit compares a negative voltage and a negative reference voltage and outputs a first output voltage from the first output terminal in response to the comparison result. The negative voltage is input to the first input terminal. A positive reference voltage is input to the second input terminal. The positive reference voltage is determined so that comparison is performed. The differential pair includes a first n-channel transistor and a second n-channel transistor each having a gate and a backgate. The first input terminal is electrically connected to the backgate of the first n-channel transistor. The second input terminal is electrically connected to the gate of the second n-channel transistor.

The charge transfer transistors of a positive or negative charge pump are biased at their gate terminals with a control voltage that provides for an higher level of gate-to-source voltage in order to reduce switch resistance in passing a boosted (positive or negative) voltage to a voltage output of the charge pump. This control voltage is generated using a bootstrapping circuit whose polarity of operation (i.e., negative or positive) is opposite to a polarity (i.e., positive or negative) of the charge pump.

A voltage doubler circuit supports operation in both a positive voltage boosting mode to positively boost voltage from a first node to a second node and a negative voltage boosting mode to negatively boost voltage from the second node to the first node. The voltage doubler circuit is formed by transistors of a same conductivity type that share a common bulk that is not tied to a source of any of the voltage doubler circuit transistors. A bias generator circuit is coupled to receive a first voltage from the first node and second voltage from the second node. The bias generator circuit operates to apply a lower one of the first and second voltages to the common bulk.

Apparatus and methods for power amplifier envelope tracking systems with automatic control of a slew rate and a mode of an error amplifier of the envelope tracking system. The envelope tracker can include a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a control circuit that controls the slew rate of the error amplifier based on the detected signal bandwidth.

Apparatus and methods for power amplifier envelope tracking systems with automatic control of a slew rate and a mode of an error amplifier of the envelope tracking system. The envelope tracker can include a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a control circuit that controls the slew rate of the error amplifier based on the detected signal bandwidth.

The charge transfer transistors of a positive or negative charge pump are biased at their gate terminals with a control voltage that provides for an higher level of gate-to-source voltage in order to reduce switch resistance in passing a boosted (positive or negative) voltage to a voltage output of the charge pump. This control voltage is generated using a bootstrapping circuit whose polarity of operation (i.e., negative or positive) is opposite to a polarity (i.e., positive or negative) of the charge pump.

Provided is a comparison circuit to which a negative voltage to be compared can be input directly. The comparison circuit includes a first input terminal, a second input terminal, a first output terminal, and a differential pair. The comparison circuit compares a negative voltage and a negative reference voltage and outputs a first output voltage from the first output terminal in response to the comparison result. The negative voltage is input to the first input terminal. A positive reference voltage is input to the second input terminal. The positive reference voltage is determined so that comparison is performed. The differential pair includes a first n-channel transistor and a second n-channel transistor each having a gate and a backgate. The first input terminal is electrically connected to the backgate of the first n-channel transistor. The second input terminal is electrically connected to the gate of the second n-channel transistor.