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# OPA541: Current slew rate specification of op-amps?

Part Number: OPA541

Hello,

I know that slew rate specifieshow fast the output voltage of an op-amp can change. But is there a measure that specifies how fast the output current of op-amps can change?

I need this information because I need to drive a capacitive load with a triangular voltage waveform. That means the the current waveform will be a square wave that swings from +Iout to -Iout.

I did a simulation with OPA541 and saw that it can it can go from +180mA to -180mA in 2us. But it's an expensive IC so I want to use a cheaper op-amp.

Here are the circuit schematic and simulation results:

• Mustafa,

The timing response of the op amp output for any large input signal will be controlled by the slew rate UNLESS the capacitive load is large enough for the short-circuit output current to be a limiting factor.  In other words, the only time output will be slower than specified slew rate if the current demand will exceed op amp maximum output current capability (Isc).  Since: Ic = C*dV/dt, assuming OPA541 max output current of 8A, the op amp output will be slower than slew rate for: CL > Ic/(dV/dt) or CL > 8A/(10V/us) or CL> 800nF - see simulation below.

Case 1: with CL of 470nF slew rate controls the output response.

Case 2: with CL of 5uF, Isc 8A limit controls the output response (see Isc clipping below).