Doubts regarding on the Avago ATF54143 transistor parameters

[pusparaga]

Dear Sir,
I want to use my design to Avago ATF54143 transistor. When I went through the datasheet of Avago ATF54143 transistor. I am getting the following doubts.

(1) He has given in the datasheet absolute maximum ratings as follows

Symbol Parameter Units Absolute Maximum
V_DS Drain-Source Voltage V 5
V_GS Gate-Source Voltage V -5 to 1
V_GD Gate-Drain Voltage V -5 to 1
I _DS Drain Current mA 120

From the above parameters, we can notice that Vgs, Vds, Vgd, Ids. He is saying in the datasheet Absolute maximum ratings of the above parameter. My doubt is , how to understand these values, whether we have to understand absolute values or potential difference values of Vgs,Vds, Vgd, Ids values.
What I understood about absolute value is , we have to take the difference of voltages with respect to the ground. Potential difference(Voltage Difference) is, we have to take differences of voltages, suppose V_GS means Vg-Vs.
If anybody knows please clear above doubts. While designing, whether we have to take absolute voltages or difference of voltages.
If we take differences of voltages(Vgs), why he has given in the datasheet Absolute maximum ratings.

 

[tony_lth]

Normally, S is connectted to GND, so its voltage is 0V.
G is connect to negative voltage, using some resistor to divide -5V or -3V, you need to adjust those resistors.
So Vgs is maximally -5V.
Absolute value and relative value both must meet the requirements.

 

[pusparaga]

Normally, S is connectted to GND, so its voltage is 0V.
G is connect to negative voltage, using some resistor to divide -5V or -3V, you need to adjust those resistors.
So Vgs is maximally -5V.
Absolute value and relative value both must meet the requirements.

tony_lth Sir,
Thank you for your help. I have the following clarifications,
(1) I agree with you. Normally , S is connected to GND, So its voltage is 0 volts. In my case , I will connect MLIN L= 1 mm and W=0.9 mm on either side "S"(source) of the ATF54143 transistor. So Some Micro volts is generating at the either side "S"(source) of the ATF54143 transistor,then do I need to take the differences of voltages Vgs(Vg-Vs), Vds(Vd-Vs), and Vgd(Vg-Vd) or do I need to take differences of voltages with respect to GND. But in my case, "S'" is not connected directly to the GND, it is connected to the MLIN with some "L" and "W". I am getting some times microvolts or volts, must I have to take the differences of the voltages. Please clarify it.

(2) What about Ids,here also have we to take the differences of the currents ( Id-Is) , can you clarify it.

(3) My third question is, if we connect the two ATF54143 transistors cascaded mode or feedback to each other, then two transistors Vgs, Vds , and Vgd must be less than or equal to the Absolute maximum ratings. Please can you clarify it.

 

[D.A.(Tony)Stewart]

Think of DC biasing the PHEMT like an NPN.

Vgs is 0.59 nom. for operation but can go -5 to +1 without damage.

ABSOLUTE MAXIMUM is not used for normal operational design, but worst case to avoid and stay clear of.