AD8338
Recommended for New Designs
The AD8338 is a variable gain amplifier (VGA) for applications
that require a fully differential signal path, low power, low noise,
and a well-defined...
Datasheet
AD8338 on Analog.com
This is regarding AD8338 I am using in VGA mode. The gain voltage set to 0.8 Volt. I am giving single input and taking single output. Deto pin Grounded. 0.1uF Capacitor connected between VREF and OFSN pins. 4.7V Power supply is given to the circuit.
200KHz, -40dBm signal is given as input.
With this configuration, I am not getting gain, no output.
Only I starts getting output when I slowly downs the gain voltage level from 0.8V to 0.6V. But, at this stage I am not getting my desired gain which is 60.
Pics and schematic is attached, What should be the change required to get desired gain of 60 with working output. My input range is 10Khz - 300KHz.
Hello Akshay1992 and JayeshU,
Apologies for the delayed response. I was out of office for a few days and just got back today.
I quickly looked on your schematic, and I would like you to implement these changes:
- When the AGC function is not used, the DETO pin needs to be connected to GND and the VAGC pin needs to be connected to pin VREF only. I would like to recommend removing C140 on the schematic.
- Since you are not using OUTM's Output, please replace R90 with a higher resistance value. (Ex. 1Meg or higher) 51ohms is too little and could cause high output current draw and high power dissipation that could raise the junction temperature above the safe levels, potentially damaging the part.
- Remove L19 and C147 and directly measure the output after C146.
Let me know the test results once you've got them.
Best regards,
Paul
Hello Akshay1992 and JayeshU,
Apologies for the delayed response. I was out of office for a few days and just got back today.
I quickly looked on your schematic, and I would like you to implement these changes:
- When the AGC function is not used, the DETO pin needs to be connected to GND and the VAGC pin needs to be connected to pin VREF only. I would like to recommend removing C140 on the schematic.
- Since you are not using OUTM's Output, please replace R90 with a higher resistance value. (Ex. 1Meg or higher) 51ohms is too little and could cause high output current draw and high power dissipation that could raise the junction temperature above the safe levels, potentially damaging the part.
- Remove L19 and C147 and directly measure the output after C146.
Let me know the test results once you've got them.
Best regards,
Paul
