O P A 0 _ I N 0 - O P A 0 _ O U T O P A 1 _ I N 0 - O P A 1 _ O U T 1 . 2 5 V R E F - + I n t e r n a l O P A 0 - + I n t e r n a l O P A 1 O P A 0 _ I N 0 + O P A 1 _ I N 0 + 2 0 . 0 k R 1 1 2 0 . 0 k R 1 3 2 0 . 0 k R 1 4 4 9 9 R 1 2 4 9 9 R 1 5