OPA847 Transimpedance amplifier with high oscilator

witat rangtain

Prodigy 60 points

Other Parts Discussed in Thread: OPA847, OPA657

Hello TI engineers

I design transimpedance Amplifier(Using OPA847) for photodiode amplifier

This circuit design on PCB surface mount but when measure it has signal oscillator and noise about 100 mV.

My oscilloscope scope is Agilent MSO6034A

Impedance load of oscilloscope is 50Ohm/14pF

And I use PIN-Photodiode Hamamutsu S6968

Please tell me what is true problem, Thank you very much

Best regards

Witat

over 11 years ago

0 Hooman Hashemi over 11 years ago

TI__Mastermind 22825 points

Hello Witat,

Is the information in this E2E post of any help to you?

http://e2e.ti.com/support/amplifiers/precision_amplifiers/f/14/t/182579.aspx

You may be able to do DC coupling from your photodiode and use a servo loop to get rid of ambient current, as outlined within the link above.

Regards,

Hooman

0 witat rangtain over 11 years ago in reply to Hooman Hashemi

Prodigy 60 points

Hello Hooman,

Thank you for answer my question but when I use this circuit, it has same effect.

I see recommend about board layout in data sheet "Minimize the distance (< 0.25") from the power-supply pins"

In my opinion, example this information

If I use regulator IC distance between power-supply pins and output regulator pin must less than 0.25"

I don't know that's right . because I use Laboratory DC power supply connect via copper length 1 m.

Best regards,

Witat

0 Hooman Hashemi over 11 years ago in reply to witat rangtain

TI__Mastermind 22825 points

Hello Witat,

Regardless of where the regulator might be in relation to OPA657, you must use decoupling caps from each supply to ground right at the pins. Most times people use ceramic 0.1uF caps, but you may experiment with multiple caps as low value caps are better for higher frequency, and vice versa.

I have recently successfully tested the OPA657 in a TIA setup that you may find useful:

http://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/p/294380/1038549.aspx#1038549

Regards,

Hooman

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OPA847 Transimpedance amplifier with high oscilator