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need a start-up circuit for high voltage design?

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dominoeff

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hi guys:
i use a simple Vbe reference circuit to bias my circuit,but it need a start-up circuit.In my process both high voltage nMOS and high voltage Pmos have a limited gate-source voltage Vgs<5 V, though the drain-source voltage can be 30V. what kind of circuit should be a solution.Thanks.
 
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You can use several diode-connected MOSFET to limit Vgs.
 

Thanks.But my power supply supply has a range form about 5.5 to 30.when the power voltage is low,serveral diode-connected MOSFET can't work.I try a RC circuit to delay the gate voltage of the pMOSFET,so can keep the pMOSFET active some time to rise the gate voltage of nMOSFET.It works but when the value of the delay Resistance and caacitor are not suitable ,the pMOSFET will get a big gate-source voltage.I am afraid the process mismatch will destroy it.
 

A high valued resistor, with suitable isolation voltage?
 

Thanks to ****_freebird
A high valued resistor, with suitable isolation voltage?
Click to expand...
The RC circuit is used to delay the gate voltage rise of pMOSFET when power is on.The delay time shuold be choosed that when it is large ,the gate voltage rise too slow ,it cause a large Vgs of the pMOSFET that will destory the device, and when it's small there will be not enough time to rise the gate voltage of the nMOSFET to active it.I set the Resistor and Capacitor value by simulation.
Thanks to erikl.
Constant current into a gate-source (resp. gate-bulk) resistor
Click to expand...
In my process, large gate-source voltage will destory my device.
 

dominoeff said:
In my process, large gate-source voltage will destory my device.
Click to expand...
Constant current into a gate-source resistor - both calculated for w.c. conditions - will limit the gate-source voltage to a safe value.
 

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