Hi everyone,. I have designed a low noise amplifier which needs + 4.4 volts and -5 volts (~10mAs) for biasing purposes. Uptill now on bench testings i was using switching DC power supplies. However now i want to integrate it with my datasystem and wondering which way i can bias my amplifier, keeping noise from the bias lines minimum. I have put bunch of bypassing capacitors close to the circuit. Should i just get some batteries & use resistors in series or if there are clean regulated DC OEM type power supplies i can mount in a small box?
Clean Biasing options for LNA
Oct 21, 2006
2 Replies
You might want to use a combination of feedthrough capacitors ferrite beads and or RC/LC filters on the power supply lines fed from any available suitable power lines, I assume it will be in its own screened enclosure, small sot23 regulators are helpfull too if theres lower frequency noise/ripple on the lines wich might cuase a problem, however I dont seem to be able to find any sot23 -5 regulaters last time I looked form my usual supplier anyway.
Colin =^.^=
Usually any LNA *MUST* be supplied from a linear clean regulator (or a ultra low noise DC switching supply as those from Linear Technologies). There are a bunch of LDO regulators in SC70 or SOT23-5 packages (at Digikey for example). Search for LDO at National and Maxim. Filtering will not help as long the noise may come on the ground from a nasty switching DC supply.
Vasile
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