All op amps used are the same Texas Instrument LM348n. The datasheet says the op amp has a nominal slew rate of 0.5 V/µs, but gives no tolerance.
I have a square signal with an amplitude of 500 mV peak to peak being sent into a two op amps system. The first op amps is a unity gain op amp. It exists to prevent the wave generator's output impedance from affecting the second op amp's gain. The second op amp is a simple inverting op amp with a gain of -10.
When I measured the slew rate of the inverting op amp alone, I found a slew rate of 0.62 V/µs. However when the cascade circuit is created, the slew rate measured at the second op amp's output is now 0.589 V/µs.
Is this decrease in slew rate due to the fact that the signal was sent through two op amps, each with its own slewing effect? Do the slew rates combine in some way?
Lastly when I set the second op amp to a gain of -1, the slew rate decreases even more to 0.414 V/µs. Is unity gain instability the reason for the second decrease in slew rate?
I thought the slew rate was an intrinsic property of an op amp. Is there a variable that affects slew rate I am not considering?