function [B,A] = boost(fs, fc, bw, gain, P);
%BOOST - Design a boost filter at given gain, center
%        frequency fc, bandwidth bw, and sampling rate fs
%        (default = 1).
%
% J.O. Smith 11/28/02
% Reference: Zolzer: Digital Audio Signal Processing, p. 124

Q = fs/bw;
wcT = 2*pi*fc/fs;

K=tan(wcT/2);
V=gain;

b0 =  1 + V*K/Q + K^2;
b1 =  2*(K^2 - 1);
b2 =  1 - V*K/Q + K^2;
a0 =  1 + K/Q + K^2;
a1 =  2*(K^2 - 1);
a2 =  1 - K/Q + K^2;
A(1,:) = [a0 a1 a2] /a0;
B(1,:) = [b0 b1 b2] /a0;

if nargout==0
  freqz(B(1,:),A(1,:));
  title('Boost Frequency Response')
end