how to improve P1dB of LNA?
时间：04-07
整理：3721RD
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Friends, I am designing a GaAs LNA. Tech is WIN (Wireless Information Networking) 0.5um INGaAs pHEMT Enhancement/Depletion-Mode Device.
The LNA requires variable gain from 0dB~18dB, P1dBin >-10dBm@18dB, 0dBm@0dB. And working frequency between 400MHz---900MHz.
I tried many kinds of circuit, such as cascade with feedback (single stage), common source with feedback + common source with feedback., common source with source degeneration + common source with feedback.
But every circuit has -20dBm P1dBin.When I decrease the gain, P1dBout does not change
Usually the current is about 4mA for every stage, VG is about 0.3-0.4V, VD is about 2.5V for 3.3V VDD. The size is about 50*8 or 75*8
Who knows how to increase P1dBin of GaAs LNA?
The LNA requires variable gain from 0dB~18dB, P1dBin >-10dBm@18dB, 0dBm@0dB. And working frequency between 400MHz---900MHz.
I tried many kinds of circuit, such as cascade with feedback (single stage), common source with feedback + common source with feedback., common source with source degeneration + common source with feedback.
But every circuit has -20dBm P1dBin.When I decrease the gain, P1dBout does not change
Usually the current is about 4mA for every stage, VG is about 0.3-0.4V, VD is about 2.5V for 3.3V VDD. The size is about 50*8 or 75*8
Who knows how to increase P1dBin of GaAs LNA?
Your LNA has a large bandwidth. Have you checked that the input and output matching (S11 and S22) are 50 ohms all over the band? In other words, your -20dBm P1dBin is always the same for all the bandwidth? Good matching mus be done with inductors and capacitors, and the gain can be increased with a higher output resistor (from +Vcc to drain-pin). Which value of resistor have you put?
Regards.
Use CasCode configuration..