Re: Ping Tester/ Complementary emitter-follower

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

Antonio,
I have posted the schematic of my ping tester at
http://hot-streamer-dot-com/temp/PING%20TESTER.jpg.
It is similar to your circuit although there are differences such as the
four-decade capacitor switch SW2 also the circuit operates over a higher
frequency range from 940Hz minimum (on Range 1) to 2.09MHz (on Range 4).

In the diagram  have shown a 555 astable although I would prefer to use the
TLC555 CMOS timer IC which works up to 2.1MHz. I know this seems excessive
but I would like to have an instrument that doubles as a squarewave
generator as well as a ping tester.

I am also interested in the possibility of inverting the output on Pin 3 of
IC1 with as second 555 (or TLC555) connected as a Schmitt trigger (Pins 2
and 6 on the second IC tied together).
  the load under test being connected across Pin 3 on IC1 and Pin 3 of IC2.
In this configuration the two IC would work together as a full-wave bridge
allowing a peak-to-peak voltage of nearly twice that possible with only a
single IC.
What will be the effect of this on crossover distortion/ step voltage when
emitter-followers are added -will it reduce the influence of the voltage
step or it worse?

With regard to the complementary emitter-follower output stage(s) what
transistor type is appropriate given a max frequency of 2.09MHz?

Finally, if an RC network is used to keep current flowing in the transistors
as they change state, what are the appropriate values for C and R again
given that the maximum frequency is 2.09MHz?

Jolyon