the paper says:
“Figure 3 shows the -3 dB bandwidth characteristic
against gain variation of the VGA. The proposed VGA
extends its bandwidth by introducing negative capacitance.
Also, it can be recognized that the bandwidth remains
almost constant in spite of gain variation as illustrated in
figure 3. Figure 4 shows the frequency characteristic when
the gain is set to 20 dB. The proposed VGA is
implemented by two stages of second-order LPF and one
stage of first-order LPF. Due to these LPFs, the proposed
VGA shows a more drastic cut-off frequency slope than
without negative capacitance technique”


i wonder why the VGA has the function of LPF