how to plot constant gain with bode

How does one plot a constant gain with bode?

The following example gives me the following error:

R1 = 81800;

R2 = 18200;

R3 = 5600;

C1 = 13e-9;

RTH = (R1*R2)/(R1 + R2);

gmmin = 100e-6;

gmmax = 1e-3;

w1 = (1/(C1*R3)); % f1 and f2 from G

f1 = w1/2*pi;

w2 = (1/(C1*R1));

f2 = w2/2*pi;

w3 = (1/(C1*RTH)); % f3 and f4 from T

f3 = w3/2*pi;

w4 = (1/(C1*(RTH+R3)));

f4 = w4/2*pi;

>> Go = R2/(R1 + R2);

>> fmin = 10; % minimum frequency = 10 Hz

fmax = 100e6; % maximum frequency = 10 MHz

% Set Bode plot options

BodeOptions = bodeoptions;

BodeOptions.FreqUnits = 'Hz'; % we prefer Hz, not rad/s

BodeOptions.Xlim = [fmin fmax]; % frequency-axis limits

BodeOptions.Ylim = {[-100,100];[-180,180]}; % magnitude and phase axes limits

BodeOptions.Grid = 'on'; % include grid

figure(2);

% define plot title

BodeOptions.Title.String = 'Go';

bode(Go, BodeOptions, 'b'); % generate the magnitude and phase responses

legend('Go')

Error using tf (line 299)

The values of the "Numerator" and "Denominator" properties must be row vectors or cell arrays of row

vectors, where each vector is nonempty and containing numeric data. Type "help tf.num" or "help tf.den" for

more information.

Error in bode (line 107)

sys = tf(a,b);

Answer 1

[Birdman]

To plot Bode of constant, define it as a transfer function but in the following way:

Gs=tf(R1/(R1+R2),1);
bode(Gs);

[hayato tsujii]

what if theres a constant out in the front

Answer 2

[Avirup]

h1=((1/(s*Cf1)*(Rf1+(1/(s*Cb1))))/((1/s*Cf1)+Rf1+(1/(s*Cb1))));

H=h1/((s*Lf1)+h1);

Re=(2*L)/((D^2)*1/fs)

zn=tf(-Re,1);%Re is simply a dc gain

zd=tf(Re,1);%Re is simply a dc gain

BodeOptions=bodeoptions('cstprefs');

BodeOptions.Grid='on';

BodeOptions.XLim=[10,500000];

BodeOptions.Ylim = {[-100,30];[-180,180]};

BodeOptions.FreqUnits='Hz';

BodeOptions.Title.String='Zn Zd Zout Plot';

bode(zout, zn, zd, BodeOptions)%this gives the bode of Dc gain, zn, zd are dc gains