PROTECTION CIRCUITRY AND METHODS FOR AUDIO GROUND CIRCUITS

Self-grounded circuitry (10) includes a signal channel conducting an output voltage (VOUT1). A charge pump (2) powered by a reference voltage (VDD) produces a control voltage (VCP). The control signal is at a low level if the reference voltage is low and is boosted to a high level if the reference voltage is high. A ground switch circuit (15) includes a depletion mode transistor (MP1) having a source coupled to the output voltage, a gate coupled to the control voltage, and a drain coupled to ground. The transistor includes a well region (4-1) and a parasitic substrate diode (D3-1). A negative voltage protection circuit (17-1) includes a depletion mode first protection transistor (MP3-1) having a drain coupled to the well region, a source coupled to a source of a depletion mode second protection transistor (MP4-1) having a drain coupled to the output voltage, the first and second protection transistors each having a gate coupled to the control voltage, and also includes a diode (MN1) coupled to charge the well region from the control voltage conductor to prevent distortion of the output voltage.