Reference startup circuit for audio amplifiers

An integrated circuit comprising:

• a processing circuit configured to process a signal with use of a reference voltage;
• and
• a reference source configured to provide the reference voltage, the reference source including a bandgap core and a startup circuit, the startup circuit including a first transistor coupled to a supply source and configured to provide a current to a reference resistance when the reference source is turned on, to thereby provide a reference voltage at a first node between the first transistor and the reference resistance, the first node coupled to a ground through a circuit that includes an electrically parallel combination of the reference resistance and a first capacitance, the startup circuit further including a second transistor coupled to the supply source through another transistor to provide a second node between the second transistor and the other transistor, the second transistor having a gate coupled to the first node, such that the second transistor is off and a startup voltage at the second node is up when the reference voltage is at or below a threshold voltage, and the second transistor is on and the startup voltage at the second node is down when the reference voltage exceeds the threshold voltage, the other transistor having a gate coupled to a source which is coupled to the second node, the startup circuit further including a third transistor implemented between the supply source and a startup node of the bandgap core, the third transistor having a gate coupled to the second node through an inverter such that the third transistor turns on to inject a startup current to the startup node when the startup voltage is up, and turns off when the startup voltage is down, the startup node coupled to the first node through a second capacitance and the electrically parallel combination of the reference resistance and the first capacitance.