Thank you for your reply.
My VGA is full differential architecture , and according to you sample ,I write sentence like this:
Vinp 2 0 dc=1.2v ac sin(0 0.5m 100meg)
Vinn 9 0 dc=1.2v ac sin(0 -0.5m 100meg)
Vctrl 4 0 dc=1.3v
And the outputs are connected to node 5 and 11 respectively
(the bandwidth is larger than 100meg for the result of vdb)
.op
.tran 10n 100n sweep vctrl 0.6 1.6 0.1
.probe gain=par('(v(11,5))/(v(2,9))')
After simulation , I change the x_axis to v(4), than I got a grotesquery waveform
1. according to fig(1),the gain is too high, it achieves 6E+24, but in vdb waveform, the gain is 7dB when the vctrl is 1.3v
2. according to fig(2),the gain is variable along with the time
MY question:
I attempt to adjust the command sentence, but it’s not effectual
Can you help me to solve the problem ?
Thank you