Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Why the drain negative voltage changed my bais?

Status
Not open for further replies.

eladg

Full Member level 3
Joined
Jan 13, 2002
Messages
185
Helped
7
Reputation
12
Reaction score
3
Trophy points
1,298
Activity points
1,237
reverse bais to fet

i built an lna with low power fet. it was single ended (one power supply , the gate is connected to gnd and sourse is connected to gnd throw resistor)

it work very good (vds =2v vgs =0.3v).
i made mistake and connectet to the drain negetive voltage.

the bais on the transistor (gaas ne321000 ) changed, and all the rf parameter changed what happend to me and why ? (the negetive voltage was 1v
 

Sounds like your transistor was damaged.
If FETs are used outside the specified values they sometimes don't stop working completely. They sometimes just alter their S-parameters.
I would encourage you to change the FET.

Regards,

Spasomat
 

Hi eladg,

The negative voltage lead to a gate current flow what will destroy your GaAs FET immediately. Such FET's are very sensitive to wrong power supply and to electrostatic discharge. So you have to change it...

Bye
 

Spasomat said:
Sounds like your transistor was damaged.
If FETs are used outside the specified values they sometimes don't stop working completely. They sometimes just alter their S-parameters.
I would encourage you to change the FET.

Regards,

Spasomat

there isnt any data about worng voltage so i donk know if it it outside the specified
 

mr_ghz said:
Hi eladg,

The negative voltage lead to a gate current flow what will destroy your GaAs FET immediately. Such FET's are very sensitive to wrong power supply and to electrostatic discharge. So you have to change it...

Bye

why i get a curent at the gate ?

at all book that i looked i sow only positive Vds
 

Hi eladg,

The NE321000 is a junction-FET. This says that there is a PN-junction between the gate and the D/S channel. If you have a negative gate bias, this diode is in reverse direction. So the current is low (below some 10s uA). If you have a positive bias (or in your case a negative channel voltage) the diode is forward biased, what leads to a relatively high gate current. This gate current distroys the gate structure.

Bye
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top