Video Amplifiers for the Mirror Screw
The
light sources for mirror screws based on my work, consist of a dozen or more of
high brightness LEDs, in colors or white, typically connected in parallel or series-parallel.
Shown here are two amplifiers, capable of handling the full range of video frequencies
for as many as 40 LEDs in various series/parallel hook-ups. The upper circuit
is one developed by Peter Smith of Scotland, member of the NBTVA and has been
well proven by the successful use by of many of the members in the NBTVA. In its
original form, the circuit could also separate sync pulses from the video signals.
In my method of operation however, sync is not required, so those associated components
have been removed. Club members are able to purchase printed circuit boards for
Peter Smith's amplifier at very low cost.
The amplifier in the lower portion of this schematic is
one I developed that uses an operational amplifier capable of providing up to
3 amperes output along with a wide frequency range. I have actually used this
amplifier successfully more than a dozen times and for as many as 36 LEDs. 
Both
of these amplifiers require a 12 to 18 volt positive DC power supply. A single
supply works on Peter Smith's circuit, whereas my amplifer requires a second negative
5 volt supply. The power supply that I use produces positve 15 volts at a relatively
high current of .3 amperes peak. It also provides a negative 5 volts at .1 amperes.
(PY)