I used PSS to simulate the opamp's 1dB compression point in SPECTRL, I found that the output signal swing is higher than vdd at the gain decreased by 1 dB comparing with small signal gain. The result puzzled me. The output voltage is distorted in large signal input. And the input signal must be large enough to make the gain decrease 1dB and now the output swing is higher than VDD.What does it mean?