Amplifier systems

Circuitry comprising:

• amplifier circuitry configured to receive a variable supply voltage, wherein the supply voltage varies according to an output signal of the amplifier circuitry;
• monitoring circuitry configured to monitor one or more parameters of an output signal of the amplifier circuitry;
• and
• processing circuitry configured to receive an indication of the voltage of the variable supply voltage and an indication of the monitored parameters from the monitoring circuitry and to apply a correction to one or more of the monitored parameters to compensate for coupling between the variable supply voltage and the monitoring circuitry.

A method for measuring coupling in a system comprising amplifier circuitry having a variable supply voltage that varies according to an output signal of the amplifier circuitry, the method comprising:

• applying a stimulus signal to cause the variable supply voltage to adopt one or more known calibration values;
• measuring a change in one or more parameters of the output signal of the amplifier circuitry resulting from a change in the variable supply voltage in response to the stimulus signal;
• based on the measured change in the one or more parameters of the output signal and the change in the variable supply voltage in response to the stimulus signal, determining an error coefficient;
• and
• scaling a value of the variable supply voltage using the determined error coefficient to generate an indication of the coupling.

An amplifier system comprising:

• amplifier circuitry for driving an electromagnetic load;
• boost circuitry for boosting a supply voltage to the amplifier;
• monitoring circuitry for monitoring a load signal driving the load;
• and
• control circuitry for determining a level of coupling between the boost circuitry and the monitoring circuitry and applying a correction to the monitored load signal.