What's the technology... discrete or inside an IC?
How low is "low current"
Speed/hysteresis requirements?
What's the input signal level?
John
What's the technology... discrete or inside an IC?
How low is "low current"
Speed/hysteresis requirements?
What's the input signal level?
John
Inside an IC, I'm designing it.
1uA
I have ~10us to make a decision, no hysteresis (yet).
0V-to-3.3V CMOS levels, out of a _very_ slow comparator....Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine Sometimes I even put it in the food
How about a couple of common-base (or common-gate) stages. Input goes to emitters; PNP base is maybe 1 volt below Vcc; NPN base is +1 from ground, both base drives weak if it's bipolars, anything for fets. Collectors/drains connected together are the output.
John
So its output is "0", "1", or FLOAT ?:-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine Sometimes I even put it in the food
It floats between input peaks. If that could be forever, add a bazillion ohm hysteresis feedback resistor from a later stage.
John
If it's a comparator, then it's nominal outputs are '0' and '1'. In your case its outputs are '0', '1' and 'confused'.
So why not just use a regular old Schmidt trigger? It'll catch the '0' and '1' cases correctly, and won't do any worse with the 'confused' cases than anything else you could cook up, unless your circuit knows more about what's going on from somewhere else.
-- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
I'd be tempted to use the power of the input signal, so common gate input structure is used to achieve simple voltage gain.
The output may look indeterminant, but it's not, it's just slow.
RL
Assuming this is a repetetive action, put a sample-and-hold in front of a Schmitt and trigger it off the back edge of the D-type clock. Of course that won't work if it's a random event.
-- John B
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