Re: High Side Pulse Transmitter

jstout@xxxxxxxx wrote...
>
> Ok, this is the current design of our high side pulse
> transmitter we are using. Please view with fixed width font.
>
> VCC
> +
> |
> .-------o------o-----------'
> | | | |
> .-. | | |
> | |2K | | |
> | | | 6V | |
> '-' | z |/
> | |< A .---|
> o---o-| | | |>
> | |\ | | |
> .-. | | | |
> | | .------|-----o o------
> | |20K | | | |
> '-' | .-. | |
> | | | | | |<
> | | | | ----|
> | | '-'200R |\
> ||-+ .-. | ___ |
> ||<- | | | .--|___|--|
> o----||-+ | | | | 10K .-.
> | '-' \| | |||
> . 100K | |-' | |
> | | <| '-'200R
> | | .| |
> |-------o------------------|
> ===
> GND
>
> The circuit should have the following features:
>
> 1. True logic; high input produces high output, etc.
> 2. Operates with Vcc from 24V to 50V.
> 3. High output is slightly less than Vcc, low is better than
> 6V less than Vcc (exa, Vh = Vcc - 0.5, Vl = Vcc - 6.0)
> 4. Riseing and falling edges should be as fast as possible.
> 5. Load is from 10mA to a maximum of 125mA, and capacitance
> from 0 to about 1.5uF.
>
> The problem with this circuit is the output bounces on the falling
> edge. Can anybody suggest a fix, or an alternate circuit?

100k is a pretty wimpy pulldown for the PNP emitter follower,
and 22k is pretty wimpy for a high-capacitance MOSFET pullup.
I can't make out the rest of the gobbled PNP pulldown circuit,
is that a pulldown current limit? All three point to trouble
with the falling edge.


--
Thanks,
- Win
.

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