[time-nuts] Power Supply Noise Affects Thunderbolt 1 PPS

[David]

The Linear Technology LT3070 (150mV @ 5A) , LT3071, LT1580 , and
LT1581 (700 mV @ 10A) are examples:

http://www.linear.com/product/LT1580

For comparison:

http://www.linear.com/product/LT1584

The LT1580 (0.8V @ 7A) has the same topology as the LT1584 (1.5V @ 7A)
except everything but the pass NPN is powered from a bias supply
brought out to a separate pin.  If the bias supply is connected to the
input supply, then it duplicates the dropout characteristics of the
LT1584.

On Mon, 27 Feb 2012 22:58:33 -0800, gary <lists at lazygranch.com> wrote:

>I hate to be argumentative, but you can't be low drop out and use an 
>emitter follower. Draw the circuit and convince yourself. You would need 
>a high side driver scheme to drive the base/gate, and that require some 
>sort of boost converter. It can be done on switchmode chips, but not in 
>a linear circuit. Well unless you ship it with a battery.
>
>On 2/27/2012 9:51 PM, David wrote:
>> The highest performance low dropout regulators I have seen use
>> emitter/source followers with a low current bias supply.