Applied Micro Circuits Corp., San Diego, hired four active domestic fixed-income managers for its $1 billion operating fund, said Scott Dawson, treasury director. The firms are: Metropolitan West Asset to manage $90 million; Strong Capital and M.D. Sass, $75 million each; and Sit Investment, $60 million, The four managers replaced three passive fixed-income managers that ran the entire portfolio; Mr. Dawson would not name the terminated managers but said the firm wanted active management. The companys remaining $700 million will be managed internally in active domestic fixed income, he said. All managers have a little flexibility to manage assets internationally, said Mr. Dawson.