[Arm-netbook] help needed with a ttl logic circuit

[Luke Kenneth Casson Leighton]

On Sun, Aug 23, 2015 at 7:24 PM, Dominique Dumont <domi.dumont at free.fr> wrote:
> On Sunday 23 August 2015 20:14:18 Dominique Dumont wrote:
>> When the input is 0, the transistor emitter is driven to ~ 0.3V which
>> should  switch off the transistor.
>
> Even better, the emitter can be driven to 0 V bby putting the 100k resistor
> before the 10k. (attached png)
>
> Hope this helps

 yeay :)

 ok so i looked up the datasheet for the 2N3904:
 http://www.mouser.com/ds/2/149/2N3904-82270.pdf

 collector-to-emitter is ~0.3 volts, base-to-emitter is 0.65 maybe as
high as 0.95 volts.

 i'm horribly confused, now.  i thought i knew how transistors worked!

 this circuit (in the section "serial") looks much more obvious, to
me.  and the Rds(ON) for low current is reported to be around 0.09v.
 http://people.physics.anu.edu.au/~dxt103/472/wspr_tx/

l.