Help with understanding QSE157 Totem Photosensor

Discussion in 'Electronics Resources' started by sonofptolemy, Nov 4, 2015.

  1. sonofptolemy

    Thread Starter New Member

    Nov 10, 2011
    Hello all,
    I'm trying to build a simple IR remote with what I have on hand. I got a pack of these nifty QSE157-ND from digikey sitting in their packages still unopened never used. I would like to use them for this simple project.

    I can start plugging them into a breadboard and fiddling with them but I'd much rather understand what the datasheet is saying first. I've taken basic electronics courses about 10 years ago, but I do not recall learning about Totem-pole outputs. In fact I can use a refresher but I'd rather do it as I go along in projects. I've searched briefly about totem-pole outputs but everything I found is an over-complicated explanation. I would rather not digress and focus on this particular application.

    Can anyone help explain this to me? How does the Totem-Pole Inverter output work and how does that differ from the other versions? Also, why does the voltage regulator only have an input and not an output? How is it regulating the voltage?
  2. sonofptolemy

    Thread Starter New Member

    Nov 10, 2011
  3. hp1729

    Well-Known Member

    Nov 23, 2015
    Totempole output is not really that amazing. Either the high side driver is on or the low side driver is on. On the voltage regulator question, yes, the drawing is kind of misleading. The output of the regulator is on the right side in all the drawings. The left side goes to ground. The "input" of the regulator is not really shown.
  4. sailorjoe


    Jun 4, 2013
    The device has three pins, one of which is Vcc, rated as 4.0 to 16.0 Volts.
    The drawing is misleading in that it takes in Vcc and stabilizes it for the LA and the Schmitt trigger, which then drive the output stage. It's correct on the 158 and 159. Threw me for minute, too.

    Totem pole output is used on lots of logic circuits. Look up almost anything in the 74xx series, and their derivatives. It works by turning on either the upper transistor or the lower one, but never both at the same time.
    Logic 1 and 0. That's it.