[Test-Equipment] Need to shift pulse up 5V

[Barry]

I think that's what the latches in the new circuitry will want but I need to do more reading on those as well as more analysis of the strobe and data signals.

Unfortunately, I do not have a full schematic and am working with what I can surmise from what I do have of it (which isn't very much...).  I do plan to go with significantly higher resistors at first as a safety factor and work my way down if necessary.

Thanks again,
Barry - N4BUQ

----- Original Message -----
> From: "Mike Manes" <mrmanes at gmail.com>
> To: "Discussion of Electronic Test Equipment" <test-equipment at mailman.qth.net>
> Sent: Friday, May 1, 2015 1:33:10 PM
> Subject: Re: [Test-Equipment] Need to shift pulse up 5V
> 
> Hi Barry,
> 
> The base is at ground, and when the NPN is saturated, the collector
> voltage can actually go >below< the base voltage in a common emitter
> configuration.  I 'd expect that in the grounded base setup, Vcb will
> come pretty close to zero. I picked the 4.7K values to set Ic & Ie to
> about 1 mA; not sure if your load sources or sinks current nor how
> much.
> 
> OK on the latching function - so the NPN will keep the strobe polarity,
> but it's not clear that's what your +5V circuitry wants.
> 
> 73 es GL de Mike W5VSI
> 
> On 5/1/15 12:05, Barry wrote:
> > I see it now. I was thinking of it incorrectly. When the NPN is
> conducting, the two equal-value resistors form a voltage divider between
> +5V and -5V and when it is not conducting, that point is seeing +5V so -
> non-inverting.
> >
> > One small point: doesn't the transistor's two diode-drops come into
> the equation effectively shifting that zero point when it is conducting?
> >
> > I have a handful of 2N3904s so I will be trying this soon and, I
> > agree
> - definitely a more elegant solution than a comparator.
> >
> > BTW, these are strobe signals that set latches so not sure if an
> inverted clock would be okay but it might. With a non-inverted pulse,
> though, I won't worry about it.
> 
> > Thanks again,
> > Barry - N4BUQ
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