Thread: MOSFET Parasitic Diode

hi, why is the parasitic diode of the MOSFET exist?

Parasitic diode is because a MOSFET does not have a PN junction. The parasitic acts almosts like a normal diode in a MOSFET process.
It is espeacially usefull in a bandgap circuit.

Hope this is what you wanted to know.

"Parasitic diode is because a MOSFET does not have a PN junction" Any detailed/further explaination on this?

Thanks

the parasitic diode of MOSFET or the body diode is the due to the PN junction formed between the source and the gate.... this usually causes latchup when left open and is connected to the lowest supply to avoid latchup but due to its reverse capacitance and diode nature it causes trouble... so generally body and source are shorted to minimise its effect...

Originally Posted by A.Anand Srinivasan

the parasitic diode of MOSFET or the body diode is the due to the PN junction formed between the source and the gate.... this usually causes latchup when left open and is connected to the lowest supply to avoid latchup but due to its reverse capacitance and diode nature it causes trouble... so generally body and source are shorted to minimise its effect...

I think u wrongly mentioned Gate instead of Body(Or bulk)..

Parasitic diode occurs because the substrate is P substrate(in Nmos) and the source and drain r n+regions.. So both the bulk and source(and drain) regions forms a diode.. When it is forward biased,it becomes an alternate path for current to flow and most of the currents may pass to the bulk instead of through the channel.. When reverse biased,it wil develop capacitance due to the inherent nature of the diode..

Originally Posted by dineshbabumm

I think u wrongly mentioned Gate instead of Body(Or bulk)..

Parasitic diode occurs because the substrate is P substrate(in Nmos) and the source and drain r n+regions.. So both the bulk and source(and drain) regions forms a diode.. When it is forward biased,it becomes an alternate path for current to flow and most of the currents may pass to the bulk instead of through the channel.. When reverse biased,it wil develop capacitance due to the inherent nature of the diode..

ya, sorry i wrote gate instead of body in a hurry...

what is the best way to minimize this parasitic? tnx.

Originally Posted by forkschgrad

what is the best way to minimize this parasitic? tnx.

Make it reverse biased so that no current flow through the diode.. For example,tie the bulk to source so that there is no forward bias for the diode as both the p and n+ region are in same potential..

But then if we reverse bias the diode, it also increases the capacitance and may make the circuit work much slower!