OPA657: Used OPA657 as a transimpedance amplifier , but it appeared self-excited oscillation,what can I do to sovled this problem？

Jerry Cao

Part Number: OPA657

This is my schematic 。First I didn't input any signal. only gave the power,and C4 is 0.4p. the OUT output 32MHz sine wave ,amplitude is 4V.

then, I change C4 to 1p . I get this sine wave.

So how can I solved the problem?

THX

over 7 years ago

0 Jerry Cao over 7 years ago

Prodigy 50 points

Supplementary explanation：I don't want my bandwidth too small. I simulate this schematic in PSpice .the band width is about 250MHz. It meet my criteria.

0 Sean Cashin over 7 years ago

TI__Mastermind 23226 points

Hi user5060131,

C2 is shorted by ground and should theoretically have no effect, but it might be affecting stability depending on your board layout. Also, R7 is not needed because it is in parallel with R5, which will complete your RC input filter. Try removing these two components.

Best regards,

Sean

0 Jerry Cao over 7 years ago in reply to Sean Cashin

Prodigy 50 points

Hi sean:

I did as you said。 The result is not satisfactory。As the picture show.the self-excited still exist.I just do a experiment board.So the ground is maybe not good.I will layout next time, Can you give me some advice in layout?

thx

jerry

0 Sean Cashin over 7 years ago in reply to Jerry Cao

TI__Mastermind 23226 points

Hi Jerry,

You should follow the design recommendations given in sections 10 & 11 of the OPA657 datasheet.

Best regards,

Sean

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OPA657: Used OPA657 as a transimpedance amplifier , but it appeared self-excited oscillation,what can I do to sovled this problem？