Operational amplifiers national semiconductor lm2904n this is the national semiconductor lm2904n dual op amp it is part of the lm158 series and features a wider operating temperature range see below applications include transducer amplifiers dc gain blocks and all the conventional op amp circuits as the device is able to operate from a single supply voltage it is possible to interface them directly to 5vdc systems without the need for additional voltages plusmn15 national semicondu