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From: MooseFET on 18 Dec 2009 22:12
On Dec 18, 8:59 am, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My-
Web-Site.com/Snicker> wrote:
> Circuit Challenge of the Day
>
> The following circuit...
>
> http://analog-innovations.com/SED/RampGenerator_Amusement.pdf
>
> is a ramp generator.
>
> It is easy to see how the upper trip point circuitry causes discharge
> of the ramp.
>
> But what causes the turn-around at the bottom?

R5 is one case where resistance is not futile. According to Ohm's
opinion, Q4 needs an extra tenth of a volt to make it stay happy.
Q1's base gets depressed by the bad mood at the collector and thus Q4
becomes sad and quits working.
From: Tim Williams on 19 Dec 2009 01:41
"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker>
wrote in message news:8enni5lkllsj5c1i0eof9rs9hb79ong690(a)4ax.com...
> You need to spend some time refining your circuit analysis/design
> tools.
>
> Don't give up your day job ;-)

Tools? What, did you actually think I'd waste a simulation on your silly
ideas? ;-)

BTW, my "day job" is doing well: I've already sold a number of induction
heater kits. :-) See the latest update on my website.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


From: Jim Thompson on 19 Dec 2009 10:51
On Sat, 19 Dec 2009 00:41:34 -0600, "Tim Williams"
<tmoranwms(a)charter.net> wrote:

>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker>
>wrote in message news:8enni5lkllsj5c1i0eof9rs9hb79ong690(a)4ax.com...
>> You need to spend some time refining your circuit analysis/design
>> tools.
>>
>> Don't give up your day job ;-)
>
>Tools? What, did you actually think I'd waste a simulation on your silly
>ideas? ;-)

"Silly ideas"? That circuit in I/C form, more than thirty years ago,
was in several different automotive ignitions.... used to time dwell.
In I/C form the ramp started essentially from zero (I could scale
transistor areas). In I/C form it was triggerable rather than
continuous, thus no R2, Q3, Q6.

That was a circuit I remembered, wanted to use again, pulled it from
archive, then couldn't figure out how it worked ;-) Stewing over it,
finally it dawned, so I made it up as a teaser to see if anyone could
figure it out. So far only one person :-(

>
>BTW, my "day job" is doing well: I've already sold a number of induction
>heater kits. :-) See the latest update on my website.
>
>Tim

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Help save the environment!
Please dispose of socialism properly!
From: Jon Kirwan on 19 Dec 2009 14:44
On Sat, 19 Dec 2009 08:51:01 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote:

><snip>
>That was a circuit I remembered, wanted to use again, pulled it from
>archive, then couldn't figure out how it worked ;-) Stewing over it,
>finally it dawned, so I made it up as a teaser to see if anyone could
>figure it out. So far only one person :-(

Oh, more than one person. But you don't read my posts. So you
wouldn't know. Regardless, I enjoyed this thread from you and thanks
for adding it.

Jon
From: Paul Hovnanian P.E. on 29 Dec 2009 14:08
Jim Thompson wrote:

> Circuit Challenge of the Day
>
> The following circuit...
>
> http://analog-innovations.com/SED/RampGenerator_Amusement.pdf
>
> is a ramp generator.
>
> It is easy to see how the upper trip point circuitry causes discharge
> of the ramp.
>
> But what causes the turn-around at the bottom?
>
> ...Jim Thompson

Q1 (and Q4) get turned on when the ramp reaches its peak. Q1 discharges C1.
When the voltage on C1 drops low enough, Q1's Vcb (a reverse biased diode)
gets forward biased. That causes Q1 to bogart all the base current flowing
through R3, leaving none for Q4 and it turns off.

--
Paul Hovnanian paul(a)hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.
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