Attila wrote:
The supplies for LNAs are usually quite benign given two constraints: * * * 1) Low frequency (0Hz to bandwidth of signal) noise is low * * * But 1) is a bit harder as it also includes 1/f noise, temperature, (upstream) supply and load effects.
The LT3042 is better in this regard than anything short of a heroic effort with discrete components, IF you use a larger-than-normal bypass capacitor on the SET pin. With Cset = 22uF, the noise density is <20nV/sqrtHz down to 10Hz. 220uF is somewhat better, but not by a whole decade because of the 1/f noise of the error/output amplifier.
The down side of a large Cset is that the power supply takes longer to reach its final voltage. A 5v supply reaches 90% voltage in about 25 seconds, and 99% in about 40 seconds. A 10v supply takes twice as long, and a 15v supply, three times. The LT3042 does have a "fast start" mode, which can reduce these times considerably (to ~0.5sec, ~1sec, and ~1.5sec, respectively) -- but still longer than usual for a regulated supply. For applications like continuously-on LNA power, there should be no problem with any of these times.
The LT3042 is a bit of a pain to use, with its buried ground/heatsink tab, but it is very good, and is the lowest noise fully integrated regulator available, AFAIK.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
