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Design >> Analog Design >> pole-zeros in the gainboost amp
https://designers-guide.org/forum/YaBB.pl?num=1237438113

Message started by zzhang on Mar 18^th, 2009, 9:48pm

Title: pole-zeros in the gainboost amp
Post by zzhang on Mar 18^th, 2009, 9:48pm

hi,all
i have design a gainboost amp: telescopic amp with two folded auxiliary amp. three amps are simulated separately. The pole-zeros are all real. But when i simulated them together as a gainboost amplifier, the first and sencond doublts which are generated by aux amp are imaginary.
my question is : why are the imaginary pole-zeros are generated and their influence about the settling of close gainboost amp.

the below is the pole-zeros of the four amp and the settling of the gainboost amp when it is used in the SHA. The GBW is about 2GHz. Can anyone give me some suggestions about how to increased the settling .

aux_n

Poles (Hz)

Real Imaginary Qfactor

1 -3.60690e+06 0.00000e+00 5.00000e-01
2 -2.22649e+09 0.00000e+00 5.00000e-01
3 -3.25471e+09 0.00000e+00 5.00000e-01

Zeros (Hz)
at V(von,vop)/V1

Real Imaginary Qfactor

1 -3.24790e+09 0.00000e+00 5.00000e-01
2 -1.52776e+10 0.00000e+00 5.00000e-01
3 1.11216e+11 0.00000e+00 -5.00000e-01

aux_p

Poles (Hz)

Real Imaginary Qfactor

1 -3.35112e+06 0.00000e+00 5.00000e-01
2 -2.61352e+09 0.00000e+00 5.00000e-01
3 -3.50438e+09 0.00000e+00 5.00000e-01

Zeros (Hz)
at V(von,vop)/V13

Real Imaginary Qfactor

1 -2.60127e+09 0.00000e+00 5.00000e-01
2 3.18942e+10 0.00000e+00 -5.00000e-01

opamp

Poles (Hz)

Real Imaginary Qfactor

1 -3.25666e+07 0.00000e+00 5.00000e-01
2 -2.03323e+09 0.00000e+00 5.00000e-01
3 -1.03461e+10 0.00000e+00 5.00000e-01

Zeros (Hz)
at V(vop,von)/V10

Real Imaginary Qfactor

1 -2.42107e+09 0.00000e+00 5.00000e-01
2 5.80142e+10 0.00000e+00 -5.00000e-01

OTA
Poles (Hz)

Real Imaginary Qfactor

1 -3.61775e+05 0.00000e+00 5.00000e-01
2 -7.96747e+08 +/- 1.16212e+09 8.84228e-01
3 -1.72790e+09 +/- 4.65469e+08 5.17824e-01
4 -2.43732e+09 0.00000e+00 5.00000e-01
5 -2.93495e+09 0.00000e+00 5.00000e-01
6 -3.43471e+09 0.00000e+00 5.00000e-01
7 -9.42222e+09 0.00000e+00 5.00000e-01

Zeros (Hz)
at V(von,vop)/V10

Real Imaginary Qfactor

1 -5.76687e+08 +/- 1.16484e+09 1.12693e+00
2 -1.76459e+09 +/- 5.70547e+08 5.25486e-01
3 -2.43079e+09 0.00000e+00 5.00000e-01
4 -3.03836e+09 0.00000e+00 5.00000e-01
5 -3.43036e+09 0.00000e+00 5.00000e-01
6 6.08141e+10 0.00000e+00 -5.00000e-01
7 -1.03276e+11 0.00000e+00 5.00000e-01

Title: Re: pole-zeros in the gainboost amp
Post by nobody on Mar 19^th, 2009, 12:53am

There was a topic named "pole zero doublet" few days ago.
It is helpful to read that post.