B
Bill Bowden
Some ideas I hear about RF amps are to decouple each stage with a
series resistor and a cap across the stage. The resistor is chosen to
drop a small voltage and the cap to have a low reactance. Next, use a
low noise device in the first stage and also separate the stages
across the board to avoid positive feedback. Another trick is to align
any tuned inductors at 90 degree angles to minimize feedback. Also use
double sided PB board to provide a good ground plane. Another trick is
to shift the phase 180 degrees with a unity gain stage to further
reduce feedback if necessary depending on layout. Is there some limit
to the overall gain of a small signal RF amp, or does it depend on the
noise generated by the circuit itself? I don't have much experience
with low noise devices. What devices are recommended (transistors, op-
amps)?
-Bill
series resistor and a cap across the stage. The resistor is chosen to
drop a small voltage and the cap to have a low reactance. Next, use a
low noise device in the first stage and also separate the stages
across the board to avoid positive feedback. Another trick is to align
any tuned inductors at 90 degree angles to minimize feedback. Also use
double sided PB board to provide a good ground plane. Another trick is
to shift the phase 180 degrees with a unity gain stage to further
reduce feedback if necessary depending on layout. Is there some limit
to the overall gain of a small signal RF amp, or does it depend on the
noise generated by the circuit itself? I don't have much experience
with low noise devices. What devices are recommended (transistors, op-
amps)?
-Bill
