ASU 4K LNAs need different biasing approach

[dpdutcher]

The 4K LNAs produced by ASU we're using for the ASO LATR OTs require a different biasing scheme than the LNF LNAs. Specifically, ASU LNAs require gate voltage = 0 and they also have different safe input ranges compared to the LNF.

• LNF
  • (min,max) values
    • Vd: (-0.5, 2) V
    • Vg: (-20, 20) V
  • optimal 4K bias
    • Vd: 0.8 V
    • Vg: -1.18 V
    • Id: 11 mA
• ASU
  • (min, max) values
  • Vd: (0, 1) V
  • Vg: (-1, 0) V
  • optimal 4K bias
    • Vd: 0.8 V
    • Vg: 0 V
    • Id: 3--7 mA

This is a must-fix, and requires changes to the config file to specify which type of 4K amp is in use, and then changes to setup_amps to bias the different amplifiers differently.

[dpdutcher]

Talking with Justin at ASU, it sounds like we can just set Vd=0.8, Vg=0 and be done with it. No adjusting Vg.