eldo_user

Optimization
Designing a Low Noise Amplifier (LNA)
number of fingers (N1) will improve noise matching, input power matching, and linearity
characteristics such as IIP3 (the current and the load values are fixed to 6mA and 200Ω
respectively).
Analyses
Using a single testbench, different analyses were simulated to extract the following key
specifications:
• An AC analysis to extract Return Loss and the Voltage Gain.
• A NOISE analysis for extracting the Noise Figure.
• A multi-tone SST analysis for the IIP3.
* Parameters
.PARAM VG=0.6 VD=1.8
.PARAM FUND1=2.45G FUND2=2.46G PIN=-50
.PARAM IS=6m ROUT=200 RS=LS/1N
VIN IN 0 RPORT=50 IPORT=1 AC 1 FOUR FUND1 FUND2 PDBM (1,0) PIN -90
+ (0,1) PIN -90
VOUT OUT 0 RPORT=ROUT IPORT=2
* Analyses
.DC
.AC LIN 11 2G 3G
.SST FUND1=FUND1 NHARM1=5 FUND2=FUND2 NHARM2=5
.NOISE V(OUT) VIN 10
.SNF INPUT=(VIN) OUTPUT=(VOUT)
* Plots
.PLOT AC SDB(1,1)
.PLOT NOISE DB(SNF) DB(NFMIN)
.DEFWAVE AV_DB=VDB(OUT)-VDB(IN)
.PLOT AC W(AV_DB)
The .DEFWAVE command was used to define the voltage gain (dB).
Design Variables
For the optimization analysis, each parameter has an initial value, together with lower and upper
bounds. For example, the capacitor CPIN1 has an initial value of 0.1p with lower and upper
bounds of 0.10p and 10p respectively. Our problem has bound constraints on the variables.
The variables LS and N1 are specified using the fourth parameter of the .PARAMOPT
command. It means that these parameters are allowed to lie only on a discretized grid (the fourth
parameter gives the step of this grid). Refer to “Eldo Optimization Methods” on page 592 for
more information, and also the “Solving Problems with Pseudodiscrete Variables” on page 668.
The design variables are specified as:
Eldo® User's Manual, 15.3 665