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

[Mike Manes]

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