How do different power supplies affect the dynamic performance of the op amp?

RobertLiang

How do different power supplies affect the dynamic performance of the op amp? [Copy link]

邀请：@maychang   @sjl2001   @huo_hu   @gmchen   参与回复

Hello Expert,

I have read in some materials that changing the circuit supply voltage may affect some dynamic performance of the op amp, such as:

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"Hello, Amplifier" electronic version - P178, series composite amplifier circuit [attach] 602531 [/attach]

"This circuit still has problems, its output signal amplitude is still small", "Changing the power supply voltage of AD8009 from the original circuit's +-2.5V to +-5V, while keeping the low voltage power supply of AD8628, can immediately obtain a higher output amplitude."

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Question: If high-voltage power supply can improve the output capability, slew rate and dynamic performance of the op amp, why should the previous stage AD8628 still be powered by low voltage?

In addition, I found in the data sheets of some op amps (such as ADA4530) that the slew rate and other dynamic parameters of the op amps are the same under different power supplies .

Correction: Under different power supplies, some dynamic parameters of some op amps may change.

Thanks!,

呜呼哀哉

The first one is not clear, and the second one is not clear to which parameter the full power bandwidth of the op amp should be attributed?

maychang

If high-voltage power supply can improve the output capability, slew rate and dynamic performance of the op amp, why keep the previous stage AD8628 still powered by low voltage?

When you power an op amp, you cannot use as high a voltage as you want. Op amps have both a maximum and a minimum supply voltage. If the supply voltage exceeds the maximum allowable voltage, the op amp will burn out, and if the supply voltage is lower than the minimum allowable voltage, the op amp will not work.

As for this specific case, the front stage is still powered by low voltage. I did not check the manual of the op amp. It may be that the front stage does not allow the use of high voltage power supply, or it may be that the front stage does not need such a high voltage.

maychang

In addition, I found in the data sheets of some op amps (such as ADA4530) that the slew rate and other dynamic parameters of the op amps are the same under different power supplies.

Different supply voltages have little effect on some parameters of the op amp, and great effect on some parameters of the op amp. It is absolutely not possible to say "other dynamic parameters are the same".

RobertLiang

maychang posted on 2022-4-26 11:51 In addition, I found in the data sheets of some op amps (such as ADA4530) that the slew rate and other dynamic parameters of the op amps are the same under different power supplies...

Thanks!

The first problem is that I ignored the maximum power supply of AD8628, which is indeed only +-2.5V. Thank you.

The second problem was my negligence. The slew rate of AD8009 was nearly twice as different when it was +-5V +-2.5V (I was looking at ADA4530 before. The slew rate of this chip did not change no matter how the voltage was supplied, so I misunderstood it).

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As for the "higher output amplitude" mentioned in "Hello, Amplifier", my guess is that it mainly depends on the two parameters of the op amp, "output swing" and "slew rate". Indeed, a higher power supply will bring some improvement.

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Thanks again for the answer!

maychang

RobertLiang posted on 2022-4-26 13:28 Thank you! The first problem is that I ignored the maximum power supply of AD8628, which is indeed only +-2.5V, thank you. The second problem is my negligence again...

As for the "higher output amplitude" mentioned in "Hello, Amplifier", my guess is that it mainly depends on the two parameters of the op amp, "output swing" and "slew rate". Indeed, a higher power supply will bring some improvement.

It doesn't matter whether you read this book or not.

Roy_hu

The VP and VN of the 2nd and 3rd pins of the rear stage U2 affect the Vout of the front stage U1.