Data Sheet

LABCENTER ELECTRONICS LTD.
236
The OUT phase trace shows the expected phase distortion at the extremes of the response,
dropping to -90° just off the right of the graph, at the unity gain frequency. The high-pass filter
effect of the input bias circuitry can be clearly seen if the U1(POS IP) magnitude trace is
examined. Notice that the x-axis scale is logarithmic, and to read values from the axis it is best
to use the cursors.
Swept Variable Analysis
It is possible with Proteus to see how the circuit is affected by changing some of the circuit
parameters. There are two analysis types that enable you to do this – the DC Sweep and the
AC Sweep. A DC Sweep graph displays a series of operating point values against the swept
variable, while an AC Sweep graph displays a series of single point frequency analysis values,
in magnitude and phase form like the Frequency graph.
As these forms of analysis are similar, we shall consider just one - a DC Sweep. The input bias
resistors, R1 and R2, are affected by the small current that flows into U1. To see how altering
the value of both of these resistors affects the bias point, a DC Sweep is used.