User Guide

The CMOS Amplifier Desi
g
n 7
-5
Gain
The amplifier design is set up to measure the spot gain
at 1 kHz (assuming that the bandwidth is much greater than this)
by performing an AC analysis and then applying the Probe goal
function:
YatX(V(Vout), 1k)
to the simulation results.
YatX is provided with your MicroSim programs. The goal
function definition is as follows:
; value at given x
YatX(1, where) = y1
{ 1 | sf xvalue(where) !1;}
YatX(V(Vout), 1k)
gives the Y value on the V(Vout) trace
for the X value corresponding to 1 k.
3 dB bandwidth
The amplifier design is set up to find the
frequency where the output has fallen by 3 dB from its low-
frequency value by performing an AC analysis (same as for
Gain) and then applying the Probe goal function:
LPBW(Vdb(Vout), 3)
LPBW is provided with your MicroSim programs. The goal
function definition is as follows:
; bandwidth of low pass response
LPBW(1, db_level) = y1
{ 1 | sf level(max-db_level, n) !1;}
LPBW(Vdb(Vout), 3)
gives the low pass cutoff value on the
Vdb(Vout) trace where the output is 3 dB below the maximum
value on the trace.
The
g
oal functions, YatX and
LPBW, are contained in the file,
msim.prb. Every MicroSim
installation includes this file.
When loadin
g
a data file into
Probe, Probe automatically
loads the
g
lobal msim.prb file
(located, by default, in your
MicroSim root directory), and
any local .prb file (located in the
workin
g
directory) correspondin
g
to the current desi
g
n.
You can freely update msim.prb
or any other .prb file with new
g
oal function definitions.
Refer to online Help in Probe for
more information on the .prb files
and Probe.