why my amplifier is oscillating?

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coolradar

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I cascade two stages of UPC2776 as a post amplifier to boost the signal from a Transimpedance amplifier. Since UPC2776 have 23dB gain and 2.7GHz bandwidth and TIA supposed to work at 70MHz, it should not be problem from bandwidth point of view.

The wired thing happened once I power up UPC 2776. Output of the second stage oscillating very badly even there is no input at the first stage. I follow the schematic from its datasheet and the circuit is built at PCB with 0603 package for inductor and capacitor.

Anyone have any guess about why this amplifier is oscillating?
 

mmm , u need to download the S paramters , of this amp and check the stability of the amp , also u need to check the TIA output impedance , and how it will drive the UPC2776

khouly
 

Yes, the s-parameter will help you to figure out whether the circuit is stable by checking the stablized factor.
 

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