13 The LM4562 Opamp
The input noise voltage is typically 2.7 nV/√Hz, which is substantially lower than the 5 nV/√Hz of the 5532. For suitable applications with low source impedances this translates into a useful noise advantage of 5.3 dB. The bias current is 10 nA typical, which is very low and would normally imply that bias-cancellation, with its attendant noise problems, was being used. However in my testing I have seen no sign of excess noise, and the data sheet is silent on the subject. No details of the internal circuitry have been released so far, and quite probably never will be. The LM4562 is not fussy about decoupling, and as with the 5532, 100 nF across the supply rails close to the package seems to ensure HF stability. The slew rate is typically ±20 V/us, more than twice as fast as the 5532.