THS4509: Occasionally abnormal oscillation waveform interference

Gabriel Wang1

Part Number: THS4509

Dear Sir

Abnormal oscillation of the op-amp circuit is shown as below.

This part is used for echo signal amplification. The center frequency is 40~60M, the bandwidth is 100M, and TI ADS58C20I is connected after the op amp

over 4 years ago

0 Alec Saebeler over 4 years ago

TI__Mastermind 24524 points

Hello Gabriel,

Could you elaborate on the 'abnormal oscillation'? I do see the resistors & their locations as you highlighted, do you have any scope images or details about the oscillation you could share?

Additionally, could you confirm this oscillation is present in a simulated circuit or in the lab on the bench with a PCB?

Best,

Alec

0 Gabriel Wang1 over 4 years ago in reply to Alec Saebeler

Genius 5045 points

Dear Alec

Thank you for your prompt reply！

THS4509 datasheet claims “Minimum Gain of 2 V/V (6 dB)",

Please help to explain: Why is the gain limited to 6db for THS4509? if I set the gain to less than 6db What will happen?

Hope to get your reply in time，thanks!

0 kai klaas69 over 4 years ago in reply to Gabriel Wang1

Guru 140200 points

Hi Gabriel,

Gabriel Wang1 said:
Why is the gain limited to 6db for THS4509?

The THS4509 is a decompensated OPAmp to enhance speed performance.

Gabriel Wang1 said:
if I set the gain to less than 6db What will happen

The THS4509 will become instable and can oscillate.

Kai

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THS4509: Occasionally abnormal oscillation waveform interference