Unwanted signal notch

Eduard Razumovsky1

Other Parts Discussed in Thread: TINA-TI, THS4521, THS4551, LM7705

Why the output signal isnt "clean" ? but with a notch

Can't figure out what i'm missing

Attached screen shot + Tina-TI simulation

Thanks

0 Michael Steffes over 4 years ago

Guru 48395 points

Hello Eduard,

I can't see anything wrong in your setup - I tried changing analysis options but no luck

In any case, you want to use the upgraded version of this part, the THS4551 (better noise, HD, and DC etc etc)

That sim looks clean,

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Eduard,

looks like output saturation and recovery distortion:

Kai

0 Eduard Razumovsky1 over 4 years ago in reply to Michael Steffes

Hi Michael

I found the THS4521 better than the THS4551 in means of slew rate & BW

At the FDA input - 10MHz signal at 0.3v - 2.7v level

0 Eduard Razumovsky1 over 4 years ago in reply to kai klaas69

Hi Kai

How can i solve it without using negative supply ?

0 kai klaas69 over 4 years ago in reply to Eduard Razumovsky1

Guru 140200 points

Hi Eduard,

eventually, by slightly increasing Vcm:

Kai

0 kai klaas69 over 4 years ago in reply to kai klaas69

Guru 140200 points

Or by adding the LM7705, which generates a negative supply voltage of -0.232V from your +4.2V supply voltage:

Kai

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