function showabs(ivar,iinp)
% make a log-log plot of variable ivar responding to input iinp

  freq=logspace(4,9,200);
  for i = 1:200
    gain(i) = equations(ivar,iinp,freq(i));
  end
  handle = figure
  loglog(freq,abs(gain))
  print(handle,'vbias.png')
