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I think we're probably just seeing the op-amp's overdrive recovery behaviour.?

On Tue, Mar 4, 2025 at 06:50 AM, Michael Dunn wrote:

I think we're probably just seeing the op-amp's overdrive recovery behaviour.?

Agreed.

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Be aware that you are also over-stressing the op-amp with the 200 ohm load.? That's 37.5 mA peak output, which it might not provide.? But I think that is unrelated to the question.

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Andy

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Hello Andy , regarding the 200Ohm load,How did you? see that I am over loading the opamp?

Could you say what measurement needs to be done and where in the datasheet I need to look for this issue to see that I am not ruining the OPAMP?

Thanks.

https://www.analog.com/media/en/technical-documentation/data-sheets/ad8033_8034.pdf

On Tue, Mar 4, 2025 at 03:39 PM, john23 wrote:

Hello Andy , regarding the 200Ohm load,How did you? see that I am over loading the opamp?

From the datasheet and a few calculations.

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Your simulation uses +/- 7.5 V power.? Let's assume the output can approach (not reach) the rails.? The output pin sees R2 = 200 ohms to a virtual ground.? 7.5 / 200 = 37.5 mA.? The datasheet shows output short-circuit current = 40 mA typical with +/- 5 V supplies.? ?That is not guaranteed.? Figure 37 shows the output saturation voltage, where the output can't source or sink any more current.? It starts limiting around 25 mA, which is less than 37.5 mA, and again that is typical.? Let's say the minimum at clipping is 20 mA, which limits your outputs to only half the supply voltages (clips at +/- 4 V because of the 200 ohm load).

Could you say what measurement needs to be done and where in the datasheet I need to look for this issue to see that I am not ruining the OPAMP?

With the circuit wired as it was simulated, see at what point the output voltage clips.? Again, keep in mind it is typical only; worst-case will be worse than what is measured.

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Andy

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john23,

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Every time you delete and re-send a message, that is one more message we receive from you.

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So far I have received 6 messages that you've sent in this topic, but only 2 remain.? You can't delete the ones in our email.? I know it can be difficult, but try to get the messages right before sending, so that you don't need to delete and re-send over and over.

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Andy

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john23,

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I uploaded this file:

which is in this group's Temp directory in Files.

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Run it, then click in the plot window, and press the Spacebar to re-load the plot settings.? It compares the circuit's actual response with the ideal derivative of the input voltage.

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You can see that the circuit fails to approximate the derivative.? The ideal output at V(out) should be the negative of the derivative of V(in), but it does not look like that at all.? So when you wrote that the circuit is "working", all I can say is that it is working extremely poorly.? It lacks the bandwidth needed to approximate the actual derivative of the input pulse.? For the 1 ns rise time, the extreme leading edge of V(out) somewhat follows the derivative of V(in), but it is in the wrong direction!? Then several nanoseconds later it swings down, and then rings.? So it is completely wrong, lacking bandwidth.

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I thought the response might have been coupling via another mechanism, but it is not that.? It is doing the best that it can, with too little bandwidth.? That's all.? Its output voltage wiggles, but wrongly.

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Andy

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Hello Andy ,I lowered the rise time to 5ns,As you can see in the attached photos. I have 437mV/14ns=31V/usec? which twice lower then?80 V/μs which described in the datasheet.

How Can I improve the slew rate performance in the circuit?
Thanks.

https://www.analog.com/media/en/technical-documentation/data-sheets/ad8033_8034.pdf

On Fri, Mar 7, 2025 at 06:25 AM, john23 wrote:

How Can I improve the slew rate performance in the circuit?

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Andy

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