# help me about slew rate

Discussion in 'Electronics Homework Help' started by KUMARA SHP, Nov 25, 2014.

1. ### KUMARA SHP

122
4
Aug 1, 2014
I need to find slew rate of given component in multi sim, home work says it is possible with properties> value tab of it,
here I have attached photo
can anyone help me
thanks

2. ### LvW

604
146
Apr 12, 2014
All opamp parameters shown in the table are linear small-signal parameters. However, the slew rate is a large-signal parameter (non-linear) - hence, it is not possible to derive any information on slewing properties from these data.
In particular, for an approximate theoretical calculation of the the slew rate we need the internal compensation capacitance (enhanced by the Miller effect) as well as the maximum possible current that charges this capacitance. Both parameters cannot be derived from the given data,

3. ### Laplace

1,252
184
Apr 4, 2010
One way to make an 'estimate' from the available data could be at the unity gain frequency. Just assume a sine wave at this frequency has maximum amplitude (rail-to-rail?) then find dV/dt at the zero crossing. That will be the slew rate (at least as derived from the available data).

4. ### LvW

604
146
Apr 12, 2014
OK - thus, we derive some information from measurements resp. simulations, right?
However, why at the unity gain frequency (with/without feedback)?
In case, we are allowed to derive the slew rate from experiments (and not from the given data only) - why not using the definition for the slew rate:
Opamp with 100% feedback and determine the maximum possible output voltage (at a fixed frequency) that does not show any remarkable distortions?

5. ### Laplace

1,252
184
Apr 4, 2010
When I had the idea that the slew rate might correlate with the unity gain frequency, I checked it against the datasheet for the NE5534. It seemed to correlate rather well. However, I just realized that the scale for Fig 3 is not V/mV as shown in the graph (in error) but V/V. So any empirical evidence of a relationship between small-signal parameters and large-signal behavior seems to have evaporated. Nevermind.

KrisBlueNZ likes this.
6. ### LvW

604
146
Apr 12, 2014
It seems the questioner is not interested anymore.

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