Can someone recommend a simple current regulator circuit that I can

bias devices like the Mini-Circuits GALI-5 with? These devices like to

run at a constant current (60 mA), and a series resistor is usually

used to approximate a constant current source. However, power

consumption is a concern in this design, so I don't want to dissipate

power in the series resistor. I was considering an LDO regulator until

I realized I need constant current, not constant voltage. Is there an

integrated current regulator that I could use that would address my

power consumption concern? Who makes it?

Thanks,

The bias inductor is often unable to provide a very high impedance, so that

the bias network shunts RF power (gain loss) and degrades output VSWR. In

those cases, the resistor also serves to raise the RF load impedance of the

bias network. Any current source you design will need to present a high

impedance beyond the frequency band of interest, unless your series inductor

can do the entire job below its self resonant point.

There are constant current designs using certain adjustable linear

regulators. The sense/set resistor is the "upper resistor" and the "lower

resistor" is your load. You'd need a regulator that has the fixed voltage

drop across the upper resistor, not the lower one. Assuming the typical

1.25V drop, at 60 mA, the resistor is only about 20 ohms. If you check your

design with a network analyzer, you might find that it maintains a high

impedance at your RF frequencies (I doubt it). Otherwise, the series

inductor has to provide all of the isolation.

Good luck

Steve