Preventing power-on audio output noise in a wireless telephone handset

A method of operating an audio amplifier, comprising the steps of:

• powering-up the audio amplifier having an audio signal amplifier;
• responsive to the powering-up step, turning on a first transistor having a conductive path coupled between a selected voltage and an output of the audio signal amplifier to which a speaker is coupled;
• then enabling the audio signal amplifier and turning off the first transistor;
• then applying an audio input signal to an input of the audio signal amplifier;
• then disabling the audio signal amplifier;
• responsive to the disabling step, turning on a second transistor having a conductive path coupled between a reference voltage and the output of the audio signal amplifier.

A wireless telephone, comprising:

• transceiver circuitry, coupled to an antenna, for transmitting and receiving radio frequency signals to and from a wireless communications network;
• baseband circuitry, coupled to the transceiver circuitry, for modulating signals to be transmitted by the transceiver circuitry and for demodulating signals received by the transceiver circuitry into baseband audio signal;
• audio amplifier circuitry, coupled to a speaker output node, comprising:
• an amplifier, having a signal input receiving the baseband audio signal, an enable input receiving an enable signal responsive to which the amplifier is enabled and disabled, and an output coupled to the speaker output node;
• a first transistor, having a conduction path coupled between the speaker output node and a selected voltage, and having a control electrode;
• a second transistor, having a conduction path coupled between the speaker output node and a reference voltage, and having a control electrode;
• and
• control logic, having outputs coupled to the control electrodes of the first and second transistors, and having an input coupled to receive the enable signal, for turning on the first transistor prior to the enable signal enabling the amplifier, and for turning on the second transistor after the enable signal disables the amplifier.