Clean Biasing options for LNA

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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?

 

[colin]

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?

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 =^.^=

 

[vasile]

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?

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