Mathcad - ee217projtodonew2.mcd

Low Frequency Stabilization
It is desirable to convert the parallel combination of the load matching network inductor and
the ballast resistor into a series combination. This has the beneficial effect of improving the
stability of the amplifier at lower frequencies, at the expense of stability at higher frequencies.
The assumption is that stability is acheived at higher frequencies because of the reduced gain
and because the small parasitic losses of the passive elements become significant
Ballast Resistor
R S
R p
L p
L S
AMP
AMP
C
50 ohms
C
50 ohms
Fig. 38: Ballast resistor conversion from parallel to series
Q LP R P , L P , ω
R P
L . P ω
Q of an L P in parallel with R P
LP2S R P , L P , ω
L LS
R LS
Q LP R P , L P , ω
1 Q LP R P , L P , ω
1
1 Q LP R P , L P , ω
LP2S R L N opt , I Copt , s , L L , ω
LP2S R L N opt , I Copt , s , L L , ω
2
1
2
2
L
. P
H
R
. P
ohm
. H L LS 6.205 nH
2
Conversion from L P and R P to L S and R S
= Series Load Inductance
. ohm R LS 7.508 ohm
= Series Load Resistance
Outputs
I Copt = 7.277 mA
N opt = 46.572
L S
C S
= 8.985 nH
= 3.334 pF
C L = 1.217 pF
L LS
R LS
= 6.205 nH
= 7.508 ohm
Optimal Bias Current
Optimal Device Size
Optimal Source Matching Inductance
Optimal Source Matching Capacitance
Optimal Load Matching Capacitance
Optimal Load Matching Inductance
Optimal Series Load Ballast Resistor