In a large bowl, cream the butter, peanut butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in bananas. Combine the flour, salt and baking soda; add to creamed mixture. , Transfer to a greased 9x5-in. loaf ban. Bake at 350° for 70-75 minutes or until toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.