k=1000;
n=1e-9;
u=1e-6;

gf = -36
gp =  0

Cf = 10*n
Ci = 10*n
Rp = 33*k
Lp = 0.5
Ri = 68*k
Rs = 1.5*k

dp=2*pi;
f=100:10:5000;
w=dp*f;
s=j.*w;

Hn = s./(Ri*Cf);
Hd = s.*s + s.*(Rp + Ri)./(Rp*Ri*Cf) + 1/(Lp*Cf);

Hf = Hn./Hd;
Hhp = s.*s./Hd;

Hinput = s*Ri*Ci./(s*Ri*Ci + 1);
semilogx(f, abs(Hf) )
% for gp = 0:0.1:1
    % Hs = Hinput.*( Rs/(Ri + Rs) + gf.*Hf./(1 - gf.*gp.*Hhp) );
    % semilogx(f, 20*log10(abs(Hs)) )
    % hold on
% endfor

hold off


