What properties of op-amps cause low slew rate? Is it best described as resistance to change? Does it have to do with the type of transistors inside the op amp, BJT vs FET? Is there some involvement of resistors or capacitors inside an op-amp? A combination of all of the above?

 

My best take on this is capacitance. Sometimes capacitance is intentionally designed into an op-amp. Only when you get to really high speeds do the type of transistors come into play. Can't remember what it's called right now but, clearing the charge out of a saturated base-emitter junction slows things down.

The amount of complication matters, too. You can do a basic op-amp with a dozen parts, but some of them have hundreds of parts and way better accuracy. There are people a lot smarter here than I am. One or two will soon describe some other causes of low slew rate.

 

What properties of op-amps cause low slew rate? Is it best described as resistance to change? Does it have to do with the type of transistors inside the op amp, BJT vs FET? Is there some involvement of resistors or capacitors inside an op-amp? A combination of all of the above?

It's primarily caused by compensation in the second gain stage to prevent phase instability. In addition to affecting slew rate, it also limits bandwidth.

But there are high slew rate opamps.

 

Slew Rate = 2 Pi F Vp (for a sine wave). This can often help you sort choices at a vendor site.

 

As dl324 noted, it's largely determined by the built-in compensation of the op amp. It takes a lot of current to charge and discharge the compensation cap and how rapidly this can be done determines the slew rate.
It has little to do with the type of transistor or their design.
Op amps with higher gain-bandwidth generally have a higher slew rate.

For comparison, comparators, which are internally very similar to op amps but have no internal compensation, have a much higher slew rate.

Also, note that current-feedback op amps don't require significant internal compensation and thus generally have much higher bandwidths and slew rates as compared to standard voltage feedback op amps.

 

It has little to do with the type of transistor or their design.

I disagree inasmuch as you might be referring to the transistor design of the op-amp. See equation 18 here: http://users.ece.gatech.edu/mleach/ece4435/tutorial.pdf

SR = IQ/Cc. IQ is a design parameter arising from the transistor bias design.

 

I disagree inasmuch as you might be referring to the transistor design of the op-amp. See equation 18 here: http://users.ece.gatech.edu/mleach/ece4435/tutorial.pdf

SR = IQ/Cc. IQ is a design parameter arising from the transistor bias design.

No, I was referring to the design or type of the transistor (such as whether it's a BJT or FET), not the design of the op amp (which does obviously affect the slew rate).

 

What properties of op-amps cause low slew rate?

Their designs.

Is it best described as resistance to change?

Output's inability to follow the input.

Does it have to do with the type of transistors inside the op amp, BJT vs FET?

No.