Chip with simple program for Toy

[Reg Edwards]

Some years back, after retirement, I bought out of curiosity a copy of
Electronics Work Bench. It was and still is the only such program I have
ever had my hands on. I think it arrived on a collection of floppies.

After a few days curiosity was satisfied. Then I junked it.
---
Reg

 

[tempus fugit]

That's how I read it too.

They only need about 6mA max to work at all.


"anonymous" <anonymous@catfarm.com> wrote in message
news:edabd.384176$Fg5.247788@attbi_s53...

"peterken" <peter273@hotmail.com> wrote in message
news:0R4bd.277227$Ti1.14313598@phobos.telenet-ops.be...

NOPE
I didn't tell you regs need 400mA to function *at all*
(wonder where you read this, jeses)
Regs of this type work with output currents from 0 upto 1A, see
datasheets


"anonymous" <anonymous@catfarm.com> wrote in message
news:TN2bd.460950$8_6.164900@attbi_s04...

Above I assume your wall wart is capable of delivering enough current,
but
as a side assumption :
As far as I seem to read, all 4 individual regs take appprox 400mA,
thus
1.6A together


My bad. Thats how I read your previous posting.

 

Mantra <mymantra@yahoo.com> wrote:
: "Confused Soul" <confused.mind@gmail.com> wrote in message news:<1096521840.683522.211960@h37g2000oda.googlegroups.com>...
:> Hello Everyone,
:>
:> I wanted to know is there any way we can find the Threshold Voltage
:> (Vt) and Flatband Voltage (Vfb) of a MOS capacitor from the CV
:> characteristics of the MOS capacitor?
:>
:> Thanks
:> ConfusedSoul

: Vt only has meaning for a MOS*FET* but not a MOS*CAP*. It's a bit
: frightening if you don't already know that.

Absolutely not true.

The capaciatance of a MOS CAP (MOSFET with its source and drain tied
together) when the voltage across is less than Vt (i.e. no inversion channel)
is very small (= Cgdo + Cgso where Cgdo and Ggso are small
overlap capacitances.)

When the voltage across the MOS CAP is larger than Vt, the channel
is inverted, the device is in the linear region, and the Capacitance is
approximately Cox * The Area of the Device (i.e. Much larger than Cgdo +
Cgso.) If you understand this, you should be able to answer your own
question now.

Someone else can help you with your question about Vfb.

Joe

 

[Airy R. Bean]

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Is it based upon successive delta-time increments, and if so, what
is the increment? What prompted the last question is an attempt
I made to create a sine-wave generator using the identity that
sin dTheta = dTheta, but I had to go for an _extremely_ small
value of dTheta (ISTR 10^ -18) before getting anything like a
decent sine wave, and even that degenerated after a few cycles.

So, these circuit simulators - what is their underlying technique
for circuit simulation?

"Roger Johansson" <no-email@home.se> wrote in message
news:Xns95857BEF795A986336@130.133.1.4...

"Reg Edwards" <g4fgq.regp@ZZZbtinternet.com> wrote:
Some years back, after retirement, I bought out of curiosity a copy of
Electronics Work Bench. It was and still is the only such program I
have ever had my hands on. I think it arrived on a collection of
floppies.
Multisim has a very bad reputation because is has a lot of bugs.
The best version of EWB is 5.c

 

[Airy R. Bean]

It's been the case in Britland for many years now, that if you
want info to build modern gear, then buy the ARRL handbooks.
OTOH, if you want a mediocre book that is many
years out of date and seems to owe more to self-congratulation than
it does to technical excellence, then go for the RSCB offering. Odd, really,
when you consider that the RSCB is a publishing corporation.

"J M Noeding" <la8ak@online.no> wrote in message
news:80u4n05115iqpga3u4igokdvusvn5bis30@4ax.com...

In 1970 I bought the latest issue RSGB Handbook, obviously a decade
before the transistors were being discovered in England, and several
decades before the spectrum analyser were applied over there. So after
a week I managed to find another person to keep the book, not sure if
he paid for the rubbish

 

[Airy R. Bean]

I'm not interested in someone else's engine - that's not the
way of the _REAL_ Radio Ham

It is _ALWAYS_ worth the effort to do things for yourself - that
is the essence of _REAL_ Ham Radio - it is the CBer and the
CBer-Masquerading-As-A-Radio-Ham who buy things
off-the -shelf!

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:kft4n0hq3qhnnum7g8e8t9egksroki493c@4ax.com...

On Sun, 17 Oct 2004 13:52:17 +0100, "Airy R. Bean" <me@privacy.net
wrote:

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Most of them (exceptions being the harmonic balance types for RF) use
the old Berkeley Spice engine developed by the good folks at the
eponymous university. The simulation package authors just adapt the
engine with their own preferences WRT to features, GUI, gimmicks etc.
So yeah, you can certainly come up with your own flavor of Spice just
by adapting the basic Berkeley engine to your tastes. It's highly
unlikely to be worth the effort, though. There's already a spice out
there for everyone - if you can find the right one for you.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Clarence]

"Steven O." <null@null.com> wrote in message
news:9vn5n0dqa2k2815r2g1geb5cnvki0bruqu@4ax.com...

Hi, all. I picked up a copy of Electronics Workbench 5 (got it
cheap), it's an old version. When I try to run it, I get a message:
"Unable to write to EWB program directory. Please change the
permissions of this directory."

Well, the directory, and it's contents, are not read-only (I checked
to make sure), nor hidden, and the files are in a directory "c:\EWB",
so there are no issues with long directory names or spaces in the
directory name. I searched the Web for this error message, and came
up with two old messages from other people who had the same problem --
but never got replies. (Well, one got a reply, which said, "Make sure
the directory is not Read-only.")

I'm running this on Windows 2000, under the Admin account. When I
tried to run it on a Win 98 machine, I got a more severe error (some
kind of memory error, generated by a Visual C++ module).

Anyone know what this is about, and how I can get this thing working!?

Thanks.
Steve O.

Select the directory and check permissions. If it's read only change them to
read write. I have only encountered this problem when someone have me what was
found to be a pirate copy of a disk. The read only files and directories were
copied as they appear on the disk. Not installed. (I discarded the bad copy.)

 

[clifto]

Roy Lewallen wrote:

(In
fact, recognizing it value, Tek spent a large amount of money and
devoted resources to development of its own internal version of SPICE,
which included schematic entry and other features before they were
available in outside commercial versions.)

You owe me a keyboard to replace the one that just died under three
quarts of drool.

--
Most dying mothers say, "I love you, son," or "Take care of your sister."
Why were the last words of Kerry's mother a lecture on integrity?

 

[Steve Evans]

On Sun, 17 Oct 2004 16:52:38 +0200, J M Noeding <la8ak@online.no>
wrote:

On Sun, 17 Oct 2004 15:00:49 +0100, "Airy R. Bean" <me@privacy.net
wrote:

It's been the case in Britland for many years now, that if you
want info to build modern gear, then buy the ARRL handbooks.
OTOH, if you want a mediocre book that is many
years out of date and seems to owe more to self-congratulation than
it does to technical excellence, then go for the RSCB offering. Odd, really,
when you consider that the RSCB is a publishing corporation.

I do not agree, and soon the RSGB is the only IARU organization I
support, have been a member from january 74. They now contribute with
a lot of useful material, but it was different earlier, as one had the
feeling that high-ranked persons or duke and knights with outdated
experience was telling you what to do.

But for Radcom, I must admit that I mainly read G3VA's "Technical
topics"

My radio club was Worcester &DARC, suppose it is not so much activity
there now...

In my limited experience over the lats 22 months Iv'e read both (well
looked through both!) and they aer both highly infromative books. Id
just give the edge to the ARRL version, it's more readable and has
more coentent, but hte RAdcom version is still well worlth having on
the shelf. I do'nt see any problem with the Brits anachronistic
attachment to valve gear.
--

Fat, sugar, salt, beer: the four essentials for a healthy diet.

 

[Steve Evans]

On Sun, 17 Oct 2004 21:15:32 GMT, Steven O. <null@null.com> wrote:

Hi, all. I picked up a copy of Electronics Workbench 5 (got it
cheap), it's an old version. When I try to run it, I get a message:
"Unable to write to EWB program directory. Please change the
permissions of this directory."

I son't remember having this problme with V5 but have since upgraded
to Multisim. I recommend you do the same. Its a mudh better program.
--

Fat, sugar, salt, beer: the four essentials for a healthy diet.

 

[J M Noeding]

On Sun, 17 Oct 2004 23:07:14 GMT, Steve Evans
<smevans@jif-lemon.co.mars> wrote:

In my limited experience over the lats 22 months Iv'e read both (well
looked through both!) and they aer both highly infromative books. Id
just give the edge to the ARRL version, it's more readable and has
more coentent, but hte RAdcom version is still well worlth having on
the shelf. I do'nt see any problem with the Brits anachronistic
attachment to valve gear.

I is really a myth, TV sets were fully transistorized in Europe
compared to USA by several years


---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

 

[Rheilly Phoull]

"smpaladin" <smpaladin@yahoo.com> wrote in message
news:6753235c.0410171702.de6d3c6@posting.google.com...

This is a depiction of a circuit that I am planning to make.
http://www.geocities.com/smpaladin/maglevcircuit.gif

It is a linear motor; Whenever a magnet is passed over the hall
sensor, it turns on the Power transistor, and therefore turns on the
Electromagnet coil. In the picture, there are only four sets of the
hall sensor/transistor/coil. In the real circuit, I am planning on
having 12 sets of them.

So will this circuit work properly? And how much power will I need?
You would think that the circuit would need a lot of power, but then
you realize that only one set of the hallsensor/transistor/coil will
be turned on at any one time.

Any advice is greatly appreciated.

OK, so all you really want to know is the current for one section. No one
can tell you unless the details of the coil and battery are shown. I.e
battery voltage and details of the coil. Always include that sort of info
when asking this type of question. Also what the device is required to do
usually helps anyone answering.


--
Regards ........... Rheilly Phoull

 

[petrus bitbyter]

<mark.mcgee@csfb.com> schreef in bericht
news:1098093805.006114.238920@z14g2000cwz.googlegroups.com...

Hi

I studied A-Level electronics about 15 years ago, and I've just got
interested in electronics again. I'm very rusty, and the truth is
that my analogue electronics was never very good anyway..

I need to amplify a signal (actually, 4 of them, one being a clock
pulse) from a digital line from an IC - it's either off - 0v or on at
1.5v, nothing complicated. I need to feed this in to a PIC
microcontroller, so it needs to be at 5v when high.

I assume I'd want to use a transistor, feeding the 1.5v signal in to
the base.

Can I take the amplified 5v signal from a resistor connecting the
emitter to gnd?

No, you will only attenuate the signal to 0-0.8V.
This circuit is known an "emitter follower" and does not amplify voltage.

I've had a bit of a google, and I never see this - only a resistor from
+v to collector, but this will invert my signal - something I don't
want to do.

That's the common way to amplify voltages. You can use a two stage
amplifier. That inverts two times so you get the right signal.

I have had a line-level converter chip recommended to me - MAX3001E,
but this is only comes in very, very tiny TSSOP format, which would be
difficult to solder up, but I'm interested in the transistor solution
as this will help me to 'swat up' a bit on my A-level electronics.
Regards,
Mark

Best thing I can advise is a LM393 or similar quad comparator. That contains
four comparators so you need only one chip. Connect the inverting inputs to
a voltage divider set to - let's say - 0.8V. A non inverting input for
each of your input signals. As the outputs are open collector you may need a
collector resistor. Depends on your PIC inputs (and their configuration.)

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.778 / Virus Database: 525 - Release Date: 15-10-2004

 

[John Popelish]

"mark.mcgee@csfb.com" wrote:

Hi

I'll check out the quad comparators, thanks for the idea. Never used
them before.

Back to transistors though, because I really should get to understand
these things. I obviously need to understand the first principals. So
if you can't amplify voltage at the emitter, that infers that the
current also isn't amplified at that point?

No it doesn't the emitter voltage swing must be less than he base
voltage swing, but the emitter current can be quite a bit larger than
the base current (by the ratio of beta).

Current is a flow rate, so where's the current going? I'd expect the
current Ic to flow through the transistor, through the emitter and on
to gnd (conventional current flow)?

And through whatever is between the emitter and ground.

I thought that Ic = Ib*Hfe
(roughly)?

Well, Hfe varies as the collector to base voltage varies, but as long
as the this voltage is above a few volts and the current is not too
large, you can think of Hfe as something like a constant.

Shouldn't Ie then = Ib+Ic?

Yes.

Therefore if I put a resistor
between emitter and gnd, I should get varying (& amplified) voltage
across it because of ohms law?
What am I failing to understand?

The effect on the base current of that new voltage drop (the one
across the emitter resistor). If the base current comes from a
current source (a current that is independent of the voltage it passes
in to), then this voltage drop does not change the base current. But
if the base current comes from a voltage source through some
impedance, then this resistor changes the voltage across that source
impedance, and thus, the base current.

--
John Popelish

 

[John Popelish]

Wong wrote:

tatto0_2000@yahoo.com (Wong) wrote in message news:<509bfe22.0410150112.7c079369@posting.google.com>...
Hi,

Is it possible to saturate the NPN BJT transistor in this biasing ?
Vcc
___
|
|
|
_| C
B |
---- Resistor ----|
|
-
| E
|---------------- Output
|
Resistor
|
|
|
---
- Ground


Since the transistor is OFF when '0' to base and hence output is '0'.
Then when '1' to base I would like to have 4.5V at the output, is that
possible to bias the transistor in saturation region (since Vce no
more <0.2V)?

OK, one more question.
If my transistor datasheet stated that the minimum hFE (DC current
transfer ratio) is 100 and the maximum is 400, can I still force this
transistor into saturation where hFE normally is 10 in saturated
transistor?

Thank you.

Yes. That beta spec applies only at some collector to emitter minimum
voltage and some maximum collector current. If the minimum collector
voltage is not met, the hfe falls dramatically, since it is reverse
bias across the collector to base junction that sweeps the charge
carriers injected into the base region by the emitter (perhaps I
should say, emitted by the emitter) efficiently to the collector (the
reverse bias collects those charges out of the reverse biased layer of
the base region). The base is called what it is because originally it
was the physical object that emitters and collectors were diffused
into from opposite sides.

Once the base voltage rises above the collector voltage, the base to
collector junction becomes forward biased, and base current diverts
directly to the collector (in addition to any feeble emitter charge
collection taking place). At some value of base collector forward
bias, the base to collector current must exceed the base to emitter
forward bias current, since there is no load resistor limiting this
current in the collector path. At that point, the hfe must be less
than 1.

--
John Popelish

 

[peterken]

try wires

on the other hand, most electronic stores have something on the shelf
or scrap a tv-set, might find some handy stuff in there too



<mark.mcgee@csfb.com> wrote in message
news:1098102991.141487.152470@f14g2000cwb.googlegroups.com...
Hi

Is there available a PCB header pin set, with matching socket which can
be assembled by an amateur without expensive specialist tools?
Regards,
Mark

 

[Andyb]

<mark.mcgee@csfb.com> wrote in message
news:1098102991.141487.152470@f14g2000cwb.googlegroups.com...

Hi

Is there available a PCB header pin set, with matching socket which can
be assembled by an amateur without expensive specialist tools?

We've always used standard 3M 0.1" ribbon cable and connectors. They crimp
together using a vice, so long as you get the cable lined up properly.....

Andyb
--
The above email address is whitelisted.
If I don't have your address already, I wont see your message.

 

[Jonathan Kirwan]

On 18 Oct 2004 03:03:25 -0700, "mark.mcgee@csfb.com" <mark.mcgee@csfb.com>
wrote:

I need to amplify a signal (actually, 4 of them, one being a clock
pulse) from a digital line from an IC - it's either off - 0v or on at
1.5v, nothing complicated. I need to feed this in to a PIC
microcontroller, so it needs to be at 5v when high.

I assume I'd want to use a transistor, feeding the 1.5v signal in to
the base.

Can I take the amplified 5v signal from a resistor connecting the
emitter to gnd?

I don't think so, as the NPN emitter will have a voltage that is lower than the
base, if it's operating normally. It doesn't invert, but the lower voltage will
be the problem.

I've had a bit of a google, and I never see this - only a resistor from
+v to collector, but this will invert my signal - something I don't
want to do.

Ah. Okay. Then you probably need a second transistor, perhaps a PNP, to
reinvert it, again. A little more complexity.

I have had a line-level converter chip recommended to me - MAX3001E,
but this is only comes in very, very tiny TSSOP format, which would be
difficult to solder up, but I'm interested in the transistor solution
as this will help me to 'swat up' a bit on my A-level electronics.

Understood. It's about how I'd feel, too, I think. (TI and others do make ICs
for level shifting, which include two power pins for the purpose, in fact. But
doing it with BJTs means you can understand the basic ideas.)

As you already know, the inverter is:

5V
|
|
\
/ R2
\
|
+-----> out
|
R1 |/c
in >--/\/\----| Q1
|>e
|
|
gnd

The above circuit assumes that 'in' is an active, low impedance drive for both
0V and 1.5V and just uses Q1 as a saturated switch, more or less, allowing the
collector to get very close to the base voltage of 0V, or probably about .2V or
so. But that only happens when 'in' is at 1.5V and turns on Q1's switching
function. And when that happens, as you already know, 'out' gets very close to
0V, which is the opposite of what you want happening.

To invert the inverter:

5V
|
|
\ 5V
/ R2 |
\ |
| |<e
+----| Q2
| |\c
|/c |
in >----| Q1 +-----> out
|>e |
| \
\ / R3
/ R1 \
\ |
| |
gnd gnd

There are actually several different arrangements. One would look more like the
first case, with a base resistor like before for Q1. But this works, too, and
it does things a little differently. In this case, Q1's base is "tacked" hard
to the low-impedance drive and thus the emitter is forced to follow closely.
This impresses a voltage on R1 which allows you to calculate a fairly precise
current that you want to flow -- roughly a 'programmable constant current' that
is presented via the collector of Q1 and is driven through R2 and Q2's base.
Now, you could add another resistor to Q2's base, too, to allow the base to
'find it's place'. But if you are careful in designing R2 and R3, it's not
really necessary -- you just make sure that there is slightly more than enough
current to force Q2's base down adequately, when calculated through R2, and
allow enough margin to operate Q2's collector current via some modestly
predicted beta.

For example,

Q1 = 2N3904
Q2 = 2N3906
R3 = 47k (perhaps stiff enough for PIC inputs)

Now, you might decide to lower R3 to make it somewhat stiffer or raise it. What
you choose here will depend some on the loading that needs to be driven. But
PIC inputs (like most micro inputs) don't require more than 10uA and 5V across a
47k yields about 100uA from which 10uA won't hurt much. But read the data sheet
and make sure about this and set the expected current through R3 to be some 10X
over the worst case you have to deal with.

Okay, so to continue. When Q2 is 'on', we'll project that the beta will be
about 50 (normally, when V(CE) is a few volts the 2N3906 is often showing a beta
4-6 times this much beta, so we can expect a V(CE) of say 0.3V at a beta of 50,
I think -- but I'm guessing here.) This suggests that the voltage across the
47k is 4.7V for a collector current of 100uA.

With a collector current of 100uA and a guessed beta of about 50, the base
current needed will be 100uA/50 or about 2uA. So, let's plan to use 4uA drive
from Q1, doubling this estimate. We know that when Q1 is 'on', the emitter
voltage will be something circa 0.7V. But with such low currents (4uA) it will
probably be closer to more like 0.5V. So, let's guess at that number for now.
The emitter of Q1 will then be 0.5V less than the base, which we know to be
1.5V, so the emitter voltage will be 1.5V - 0.5V or 1.0V. We know that we want
about 4uA emitter current (this transistor's beta will be pretty high, so the
base current will be negligible) and thus, R1 = 1.0V/4uA or 250k.

Now, R2 will need to provide about 0.6V (another guess, I'm making) at 2uA (it's
'half' of the allotted 4uA.) So, this implies R2 = 0.6V / 2uA or 300k.

So, let's try:

R1 = 220k (a little more drive current, just in case)
R2 = 270k (to suck up just a little more of that drive current)

We have a design?!

5V
|
|
R2 \ 5V
270k / |
\ |
| |<e
+----| Q2
2N3904 | |\c 2N3906
|/c |
in >----| Q1 +-----> out
|>e |
| \
\ / R3
R1 / \ 47k
220k \ |
| |
gnd gnd

How does this simulate? Well, I get about 0V to 4.9V swings on the output,
given 0V to 1.5V swings on the input. And it looks pretty clean. Simulated
estimates are:

Q1 base current average of some 20pA with spikes on the transitions reaching as
much as 1.5uA (chances are, your drive to this circuit can handle that.) I(R1)
is more like 4.5uA instead of the 4uA we planned. But R1 is 220k instead of
250k, too. So we expected something extra here. I(R2) is about 2.2uA, instead
of the planned 2uA, but again we had adjusted it down a bit to suck up some
extra -- and it does. Base current on Q2 is about the same, 2.2uA (the
unaccounted for 0.1uA is actually just rounding errors I'm making.) Collector
current on Q2 is very close, too, at a bit less than 105uA.

In other words, it's seems to hold up.

But none of this takes care of speed issues. You didn't mention how fast your
logic and clock pulses may be.

If you want something with active drive HI and LO and that is faster, try
something along these lines:

R3 || 2200pF
,------------/\/\----||--------------,
| 470 || C2 |
| |
| 5V 5V |
| | | |
| | | |
| | 1N4148 | |
| \ D1 --- |
| / R1 / \ | 5V
| \ 22k --- | |
| / | | |
| | | | |
| | | | |<e Q2
| +-------------+------+-----| 2N3906
| | |\c
| 1.5V | |
| | |/c Q3 |
| '------| 2N3904 |
| |>e |
| | |
| | |
| ,-----+ +---> OUT
| | | |
| | \ |
| | / R2 |
| C1 --- \ 22k |
| 470pF --- / |
| | | |
| | | |
| | | R4 |/c Q1
IN >---++--------+-----+----------/\/\------+-----| 2N3904
| 10k | |>e
| | |
| C3 | |
| R5 || 1000pF | |
'-----------/\/\----||--------------' gnd
750 ||

In this case, R3+C2 as well as R5+C3 are "speed up" sections to help propagate
an edge forward. The rest is interesting to read through and get an eye to how
it works.

I haven't been careful about the designing the values here, because I've no idea
if you really care about something like this. Also, it again is an inverter and
you'd need to take some care about making this into a non-inverting circuit.
The point is mainly that for fast circuits you may need to do a little more than
something dead simple.

Jon

 

[Peter Bennett]

On 18 Oct 2004 04:31:36 -0700, "mark.mcgee@csfb.com"
<mark.mcgee@csfb.com> wrote:

Current is a flow rate, so where's the current going? I'd expect the
current Ic to flow through the transistor, through the emitter and on
to gnd (conventional current flow)? I thought that Ic = Ib*Hfe
(roughly)? Shouldn't Ie then = Ib+Ic? Therefore if I put a resistor
between emitter and gnd, I should get varying (& amplified) voltage
across it because of ohms law?
What am I failing to understand?

The absolute voltage on the base, relative to some random ground
somewhere, is not relevant. What really matters, and what determines
the collector current is the _relative_ voltage between base and
emitter.



--
Peter Bennett VE7CEI
email: peterbb4 (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Steve Nosko]

"Airy R. Bean" <me@privacy.net> wrote in message
news:2tfcfdF1v0f9kU1@uni-berlin.de...

I'm not interested in someone else's engine - that's not the
way of the _REAL_ Radio Ham

It is _ALWAYS_ worth the effort to do things for yourself - that
is the essence of _REAL_ Ham Radio - it is the CBer and the
CBer-Masquerading-As-A-Radio-Ham who buy things
off-the -shelf!

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:kft4n0hq3qhnnum7g8e8t9egksroki493c@4ax.com...
On Sun, 17 Oct 2004 13:52:17 +0100, "Airy R. Bean" <me@privacy.net
wrote:

Question - what is the internal modelling technique used
by these various programs, and can we produce our own package?

Steve (Evans),
Correct me if I am wrong (like I need to say this here, eh?)
I believe the underlying basis is the collection of loop / node equations
used (by Engineers) to model circuits. We know the behavior of resistors,
inductors and capacitors and have mathematical models for them. To this we
add the active devices, etc. and develop an "engine" which does all the
calculations for us. [[we used to do them by hand/slide rule -- yes, I am
included in this we]]. These loop and node equations provide us with a
mathematical model of the behavior of electronic circuits. If done
carefully, this is a general purpose model which applies to all the
situations for which our component models are valid.
Some time later there were bare engines into which we had to type the part
values and node numbers (the sane things you can see in printouts from
Spice). As computers got more powerful, schematic entry was developed. I
believe these programs to be very useful, but as with any model or
simulation, it is best to understand the limitations.
Thre is an alternate method. It is also possible to derive equations for
each type of situation and use these calculations each time you need to
solve that type of problem. I am sure you are familiar with the equations
for things such as parallel capacitors and resonance and so forth. These
are specific solutions of the properties of components in those specific
circuits.
From some postings here I get the idea that Reg is providing various
"calculators" in the form of computer programs for hams to use to
solve/design various circuits. Not one thing wrong with either this or the
general type of software...Except that the limitations argument applies to
all calculations and it is our responsibility to determine whether or not
our situation is adequately covered by a particular math model.
I am also not familiar with the programs mentioned here (except to have
heard the names), except for OrCad's PSpice ver 9, which is relatively easy
to use (for me) and provides results adequate for my purposes--not to
mention the fact that I was given a CD with the student sample version on
it). I was introduced to is by the department chair at the county college
where I was asked to teach some classes and like it. I just draw a circuit
and can then do various forms of analysis. I modeled a recent project and
all worked the first time when I assembled the one and only unit. It was a
simple RS-232 to Kenwood TH-F6A handheld interface.

I agree 100% with Reg in that a circuit simulation program is not intended
to *teach* circuit theory, That needs to come first, then the simulation
tool can help us gain a better understanding by letting us try out the
things we learn and "see" them happen with out having to collect all the
parts and wire it up. I find it much faster to "assemble" a PSpice circuit
and test my design ideas than go into my basement and collecting all the
parts.

BTW it *IS* the cap AND diode which cause the negative voltage in the
coupling circuit described so long ago...

Airy,
While I applaud your desire to understand how these "engines" work and
perhaps build your own, I suggest that it is a most formidable task by any
measure. If you understand the concept of loop and node equations then you
know the math. Now figure out how to write software to handle any circuit
and you have it...then there is the user interface...(what I believe is the
most important [and most difficult to do well] part of any program)

73,
--
Steve N, K,9;d, c. i My email has no u's.