Hello, I have bought an amplifier shown below.However when I am trying to test if my VDD is shorted to GND my measuring i get the DMM beeping as if the VDD is shorted to GND. ash shown in the layout below
Also when I measied the resistance across C2 capacitor I see only 1.6ohm.
DId I get a faulty component?
Thanks.
A video of me doing the test is attached in the link.
Thanks.
https://www.minicircuits.com/pcb/98-pl771.pdf
https://www.minicircuits.com/WebSto...o0IgWenwgd_y056U_ftvRuC5rgiL5QeNqO8nX58qABDuF

https://technionmail-my.sharepoint....YiIsInJlZmVycmFsTW9kZSI6InZpZXcifX0=&e=mXZlhF

 

Neither of those measurements are useful. A continuity test has an unknown threshold, and a capacitor should read 0 Ohms instantly and then increase steadily as it charges. But it cannot be measured that way in circuit because current is flowing through other components.

 

OMG, people working with modules but with seemly little concept of basic circuits and circuit testing methods.

This is what happens when you treat hardware like software.

Don't think about the black box, just use it.

 

Schematic:
Power ON/OFF sequence is a pain.

 

Neither of those measurements are useful. A continuity test has an unknown threshold, and a capacitor should read 0 Ohms instantly and then increase steadily as it charges. But it cannot be measured that way in circuit because current is flowing through other components.

so how can I know if Vdd is not shorted to ground?

 

so how can I know if Vdd is not shorted to ground?

What are you using for power?
Link to this module?

 

so how can I know if Vdd is not shorted to ground?

Use a current (power) limited power supply for the circuit per the unit datasheet if you suspect problems.

 

This is what happens when you treat hardware like software.

Working with modules you don’t understand is no better in the software world.

 

Hello ,I have built a biasing sequencer for this circuit, the sequence is displayed in the scope photo below.
do you think this sequence will work properly for the amplifier ?
It wont get burnt when the following sequence will be connected to it?
Thanks.

 

do you think this sequence will work properly for the amplifier ?

The sequence doesn't mention the timing but try adding more delay so VG1 is fully at -2V before turning on VG2.
Like you show between VG2 and VDD.

 

Also when I measied the resistance across C2 capacitor I see only 1.6ohm.

This is certainly possible. GaAs power FETs (depletion mode) are in on-state at 0V gate-source voltage (Vg1=0V), hence the need for a -2V pinch-off voltage at Vg1 as the first step during the power-on sequence to avoid burn-out. GaAs power FETs are also notoriously unstable at low Vds voltages, which is why Vg1 is adjusted for the proper Id value after Vdd (=Vds) and all the other voltages have been turned on and have stabilized.

Apply -2V at Vg1 and measure again. The "low resistance" across C2 should be gone.

 

Hello ,When Vg2 is 5 Vg1 is only -1.67.is there something in the datasheet regarding the "minimal error" allowed so my amplifier wont burn?
https://www.minicircuits.com/pdfs/PMA5-83-2W+.pdf

 

Hello ,When Vg2 is 5 Vg1 is only -1.67.is there something in the datasheet regarding the "minimal error" allowed so my amplifier wont burn?

I didn't see anything regarding that. Can't you delay the +5 volt signal as mentioned previously?
What circuit are you using to generate those delayed voltages?

 

No, there is nothing in the datasheet that would indicate if Vg1 = -1.67 V is OK or not. Are you willing to experiment on such an expensive chip?

 

Hello,I am using the attached circuit.
I have electrolithical capacitors which are C4 and C2.
i dont have 60u but i have 20u and 40u,I'll try to connect in parralel to increase capacitance

Ltspice file is attached.

 

Hello,I have shifted the Vg2 signal as shown in the photo.it wont burn now?
after the initial setting ,I need to to tune Vg1 for the desired current.
two questions:

1.How do I know the desired current?
2.can I meause the drain current with the device shown below.
https://www.minicircuits.com/pdfs/PMA5-83-2W+.pdf

 

Hello,I have shifted the Vg2 signal as shown in the photo.it wont burn now?

Still not quite the suggested pinch-off voltage. It may work or it may not. My advice, stick to the datasheet.

after the initial setting ,I need to to tune Vg1 for the desired current.
1.How do I know the desired current?

400mA quiescent current looks reasonable for class-A operation and max. 30 dBm output power. Unless you need way less power or are gonna run the amp in class-AB, stick to the value from the datasheet. Drain current will increase if you drive the amp towards 1W or even beyond.

2.can I meause the drain current with the device shown below.

You need a multimeter with DC current capability. No way to tell if the depicted current clamp is suitable or not.

 

Hello ,In my sequencer circuit I have Vg1 Vg2 Vdd and GND pins.
So I need to see which amongst those 16 pins is GND which is Vg1 and Which is Vg2 and Vdd,
There are writings neer the pins of Vg1 these two pins are connected according to the DMM.
But you said that DMM is not the proper tool to test shortcircuit here.
in the documentation attached they also wont say at what exact pins I connect Vg1 Vg2 Vdd and Gnd.
What could be done?
Thanks.


https://www.minicircuits.com/pcb/WTB-PMA5-83-2WC+_P02.pdf

 

But you said that DMM is not the proper tool to test shortcircuit here.

I didn't.

in the documentation attached they also wont say at what exact pins I connect Vg1 Vg2 Vdd and Gnd.
What could be done?

There are clear, visible markings either etched into the copper or printed on the board for all bias, supply and GND connections. Easy to check and confirm with a multimeter.

 

In the gerber file photo there is only the circle which marks the first pin.
How can I know for each connection in the layout shown in the picture to what pin it connects to the chip?
Thanks.

https://www.minicircuits.com/gerber/TB-PMA5-83-2WC+.zip