Hello everyone,
for our telecom system, we need to cascade two selected amplifers (hmc618a, 1700 - 2200 MHz tuned) in order to obtain more than 30 dB gain.
We thought to follow the datasheet reference design.
Are there some guidelines or issues we have to know to do that? Or Have you some advices?
Could the two cascaded stages oscillate?
Many thanks.
best regards,
Antonio L.
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