Patent ID: 9099967
Filing Date: 2015-08-04
Classification: H03F,H04R

Abstract:
1. An audio apparatus comprising: an audio source; an audio connector having a signal out pin and a return pin to be connected to an external audio load; a differential input amplifier having a signal input coupled to the audio source, an output coupled to the signal out pin of the connector, and a feedback input; a variable resistor circuit to provide a variable resistance that is within a range of 1 to 60 Ohms between a first node and a second node, the variable resistor circuit having a control input for setting the variable resistance, wherein the first node is directly connected to the return pin of the connector and to the feedback input of the differential input amplifier, and the second node is directly connected to a ground plane of the apparatus; a switch circuit having a first terminal coupled to the first node, a second terminal coupled to the second node, and a control input for setting the switch circuit into an open state and a closed state; and a load detector having outputs that are coupled to the control inputs of the variable resistor circuit and the switch circuit, wherein the load detector is used to detect the type of external audio load that is connected to the connecter and on that basis a) set the switch circuit into one of the open state and the closed state, and b) set the variable resistance.