Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
Subject: Re: Problems with Electronics Workbench
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Date: Sun, 6 Oct 2002 19:51:06 +0100
NNTP-Posting-Date: Sun, 06 Oct 2002 19:51:10 BST
"Paul Burridge" wrote in message
> Hi all,
> Sorry if this has cropped up before, but I've been getting some
> totally ridiculous solutions when trying to simulate circuits with EW.
> Despite the plaudits heaped upon it by the guy who wrote the manual, I
> can't see how one can just throw away the breadboard and rely upon it
You can't in general. Simulation is only a tool. However, 10,000
transistor analogue i.c.s have been designed with 1st pass success on
The circuit in question was an RF power amp. It didn't even
> seem to recognize that 8kv was outside the working scope of a typical
> junction transistor's Vceo! Has anyone else had problems in using EW?
This particular issue is not related to EWB, and is not considered a
"problem" by knowledgeable designers. It is related to the spice models
used. Basic spice transistors do not model Vceo breakdown. If you
require a more accurate model, you will have to build one up.
You seem to be under the are under the impression that that spice knows
everything. It don't. You still have to think!. You need to gain an
understanding of *any* tools that you are using, whether it is an
oscilloscope, side cutters or power supply. For example, you don't
expect a real voltage source to be able to supply 10,000 amps, yet you
would hardly complain that the 12V HP you bought with an output
impedance of 10mohms had a limited current output. You accept that there
is some idealizations involved.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.