Guidelines for two cascaded amplifers (hmc618a)

Hi Anton*89,

Yes, the two cascaded gain stages could oscillate if the oscillatory criterion are met. To minimize the chances of that happening, I recommend that you try to maintain a good match between all RF ports to minimize reflections and maintain isolation between the DC bias networks by not ganging together the drains. Follow closely the layout shown on our EVB, using the gerber files found here: 

http://www.analog.com/media/en/technical-documentation/evaluation-documentation/gerber-files/HMC618_1700-2200MHz-HMC618A-HMC717-HMC717A-Gerber.zip

Possibly include provisions on your PCB to increase the RF isolation between the DC bias networks of the two amps and make sure to provide adequate capacitive bypassing for each amp.

Regards,

SMcBride

Hi Anton*89,

Yes, the two cascaded gain stages could oscillate if the oscillatory criterion are met. To minimize the chances of that happening, I recommend that you try to maintain a good match between all RF ports to minimize reflections and maintain isolation between the DC bias networks by not ganging together the drains. Follow closely the layout shown on our EVB, using the gerber files found here: 

http://www.analog.com/media/en/technical-documentation/evaluation-documentation/gerber-files/HMC618_1700-2200MHz-HMC618A-HMC717-HMC717A-Gerber.zip

Possibly include provisions on your PCB to increase the RF isolation between the DC bias networks of the two amps and make sure to provide adequate capacitive bypassing for each amp.

Regards,

SMcBride