User Guide

The CMOS Amplifier Desi
g
n 7
-3
The Parameters
For this example, there are three circuit values that you must
optimize, and three corresponding parameters that the PSpice
Optimizer will vary:
• channel length for M1 (W1)
• channel width for M1 (L1)
• bias current for M3 and M4 (Iref)
Parameterized expression assi
g
nments
In the
schematic, you can see the parameterized component values for
MOSFET M1 (
W={W1}, L={L1}) and the current source I1
(
{Iref}).
In preliminary tests, the parameter values W1 = 75 m, L1 = 5 m,
and Iref = 100 mA produce the following performance
characteristics:
These initial parameter values yield both excess gain and
bandwidth, so a reduction in power consumption appears
feasible. But because the gain, bandwidth, and power depend
nonlinearly on circuit parameters such as transistor dimensions,
manual optimization is impractical.
gain 23.8
bandwidth 2.2 Mhz
power consumption 2.2 mW