Mail Archives: geda-user/2012/07/14/11:27:31
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On 14/07/12 15:48, Edward Comer wrote:
> If it is a mosfet the gate should appear to behave like a small
> capacitor (WRT one of the other pins). Do you have a capacitance meter?
> - No, I have no capacitance meter. However, given that the E-B
> junction has no conductivity in either direction, it would appear to
> be MOSFET. Additionally, its function in the circuit is as a binary
> switch of up to 500ma @ 5V. MOSFET would be good for such a purpose.
> So given the E-B behavior and the intended function, I still suspect a
> MOSFET. I was hoping that the "MON" would mean something meaningful
> other than my assumption of "MO" - "N" channel.
>
> - I do have another circuit that I was working that has a
> microcontroller with the markings removed.My favourites are the parts
> with numbers sanded off...
>
> Does the circuit still work? If so you could probably get a good idea
> of the function of the part with a little careful observation of the
> circuit in operation.
> - Yes, fully functional, which is the basis of my assumptions
> mentioned above. I intend to clone the portion of the circuitry that
> has the MON SOT-23 chip and I was just hoping that the "MON" would
> actually identify the chip more precisely.
>
> - I don't think that the photo adds anything of value but it is at
> this link:
> http://www.flickr.com/photos/23036115 AT N03/7568124520/
>
> - The link below has the portion of my reverse engineered schematic
> that has the MON marked transistor, which is identified as Q2. It is
> not, as far as I know, a BSS123 - that SYM was just handy.
> http://www.flickr.com/photos/23036115 AT N03/7568162370/
>
> - If no one knows exactly what it is, I intend to substitute a FDV303N
> for it, in my cloned design:
> http://www.fairchildsemi.com/pf/FD/FDV303N.html
>
If the substitute part can cope with your observations on the working
board, there's not much to worry about unless very high speed switching
is of interest.
Best of luck!
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<div class="moz-cite-prefix">On 14/07/12 15:48, Edward Comer wrote:<br>
</div>
<blockquote
cite="mid:1342277285 DOT 73961 DOT YahooMailNeo AT web65901 DOT mail DOT ac4 DOT yahoo DOT com"
type="cite">
<div style="color:#000; background-color:#fff; font-family:arial,
helvetica, sans-serif;font-size:12pt">
<div style="font-family: arial, helvetica, sans-serif;
font-size: 12pt; "><span style="font-family: 'times new
roman', 'new york', times, serif; font-size: 12pt; ">If it
is a mosfet the gate should appear to behave like a small
capacitor (WRT one of the other pins). Do you have a
capacitance meter?</span><br>
</div>
<div><span><font face="times new roman, new york, times, serif"
size="3">- No, I have no capacitance meter. However, given
that the E-B junction has no conductivity in either
direction, it would appear to be MOSFET. Additionally, its
function in the circuit is as a binary switch of up to
500ma @ 5V. MOSFET would be good for such a purpose. So
given the E-B </font><font face="times new roman, new
york, times, serif">behavior</font><font face="times new
roman, new york, times, serif" size="3"> and the intended
function, I still suspect a MOSFET. I was hoping that the
"MON" would mean something meaningful other than my
assumption of "MO" - "N" channel.</font></span></div>
<div style="font-size: 12pt; font-family: arial, helvetica,
sans-serif; ">
<div style="font-size: 12pt; font-family: 'times new roman',
'new york', times, serif; ">
<div id="yiv1319957895">
<div style="font-family: 'times new roman', 'new york',
times, serif; "> <br>
- I do have another circuit that I was working that has
a microcontroller with the markings removed.My
favourites are the parts with numbers sanded off...<br>
<br>
Does the circuit still work? If so you could probably
get a good idea of the function of the part with a
little careful observation of the circuit in operation. </div>
<div style="font-family: 'times new roman', 'new york',
times, serif; ">- Yes, fully functional, which is the
basis of my assumptions mentioned above. I intend to
clone the portion of the circuitry that has the MON
SOT-23 chip and I was just hoping that the "MON" would
actually identify the chip more precisely.</div>
<div style="font-family: 'times new roman', 'new york',
times, serif; "><br>
</div>
<div style="font-family: 'times new roman', 'new york',
times, serif; ">- I don't think that the photo adds
anything of value but it is at this link:</div>
<div><a moz-do-not-send="true"
href="http://www.flickr.com/photos/23036115 AT N03/7568124520/">http://www.flickr.com/photos/23036115 AT N03/7568124520/</a><br>
</div>
<div><br>
</div>
<div>- The link below has the portion of my reverse
engineered schematic that has the MON marked transistor,
which is identified as Q2. It is not, as far as I know,
a BSS123 - that SYM was just handy.</div>
<div><a moz-do-not-send="true"
href="http://www.flickr.com/photos/23036115 AT N03/7568162370/">http://www.flickr.com/photos/23036115 AT N03/7568162370/</a><br>
</div>
<div><br>
</div>
<div>- If no one knows exactly what it is, I intend to
substitute a FDV303N for it, in my cloned design:</div>
<div><a moz-do-not-send="true"
href="http://www.fairchildsemi.com/pf/FD/FDV303N.html">http://www.fairchildsemi.com/pf/FD/FDV303N.html</a><br>
</div>
</div>
<br>
</div>
</div>
</div>
</blockquote>
<br>
If the substitute part can cope with your observations on the
working board, there's not much to worry about unless very high
speed switching is of interest.<br>
<br>
Best of luck!<br>
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