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Discrete LDO
Aug 13, 2013
6 Replies
Is it stable with capacitive loads? That's the bane of p-channel LDOs.
Here's one I did. The in/out differential is only a few tenths of a volt, so the fet is behaving like a variable resistor more than a controlled current source, which really changes the dynamics. The reference is pulsed just to observe the loop response.
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
OOps, left out the link!
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John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
I'd say 'good oscillator', but it isn't very good at that either..
Tim
-- Deep Friar: a very philosophical monk. Website:
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It wasn't with a 10uF capacitive load, but adding a ~1n bypas across R2 stops the oscillation.
Depending on the Vbe of Q2 for overcurrent protection means both that the current limit will vary with temperature, and that you'll be at 0.6 -
0.7V dropout when you're flowing max current at room temperature.
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
For low headroom current sensing, do this...
but remove the hysteresis and balance the two device currents. ...Jim Thompson
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