ADA4817 self-oscillation

Question

Hi, 
 I use ada4817-1 and adg1414bcpz to convert current to voltage. 
 But the amplifier self-oscillate at frequency about 80MHz. 
 How can i cancel the unexpected frequency? 
 In attchment, ADA4817-1 convert current in DUT to voltage. ADG1414BCPZ used to 
 select feedback resistor to make gain variable.

OliverSedlacek · Accepted Answer

The ADA4817 is a very high speed part, so it needs extreme care. i would try the following: 
 Firstly, I would have the highest impedance feedback network (C221 and R88) permanently in circuit and not switched by the ADG1414. The other feedback networks would need some adjustment to component values to compensate for the fact that they are now in parallel with C221 and R88. C221 and R88 should be routed with the shortest possible tracks to the ADA4817. 
 Secondly I would add additional decouplers to the ADA4817 to work at frequencies above 10MHz. Your schematic does not indicate the dielectric type or chip size for C21 and C22, but their resonant frequency is probably below 10MHz. You should add something like a 470pF NPO capacitor in an 0402 size to decouple the supplies at frequencies above 10MHz.)

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ADA4817 self-oscillation