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-   -   extra transistor in level shifter (http://www.diyaudio.com/forums/class-d/110799-extra-transistor-level-shifter.html)

Tekko 27th October 2007 10:14 AM

extra transistor in level shifter
 
What does this NPN transistor do in th level shifter ?

In simulation it doesent do a thing. :confused:

schematic

Pabo 27th October 2007 11:26 AM

I think it keeps the LIN input on the driver high during startup which charges the bootstrap capacitor. Will give a large pop noise though so I recommend a relay to the speaker with a few seconds delay.

I am not sure how IRS2011 works but you can try to charge the bootstrap capacitor directly from the positive rail instead with something like 20k or so. Remember to check if the boot strap supply has built in zener protection across it.

Eva 27th October 2007 11:30 AM

It forces comparator output low for a brief period of time at power up.

Tekko 27th October 2007 11:32 AM

Ah ok.

Im not gonna use it so i hope the amp starts anyways.

Btw 1N4148 is not usable to charge the bootstrap eh ? I figure BYV26-150 is atleast whats needed, right or wrong ?


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