Voltage drop at second stage LNA
时间:04-04
整理:3721RD
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Hell everyone. I've been designing a 3-stage LNA for 2.4 GHz and today I tested the LNA but for some reason when I connect the LNA to voltage source it voltage supply drops from 4V(correct value) to 2.7V.
Then i used seperate voltage sources for 3 seperate stages and it seems the second stage voltage is dropping down. All the stages are equal hence i cascaded them , not a single thing is different from the other stages. So does anyone have an idea about the cause of the problem ? I checked the resistors that divides the voltage and they are fine. Could it be the dc block capacitor is not working between the first and second stage ?
Then i used seperate voltage sources for 3 seperate stages and it seems the second stage voltage is dropping down. All the stages are equal hence i cascaded them , not a single thing is different from the other stages. So does anyone have an idea about the cause of the problem ? I checked the resistors that divides the voltage and they are fine. Could it be the dc block capacitor is not working between the first and second stage ?
Resistor divider in the supply? Not good. Does your
calculation of "OK" include the LNA's DC current draw,
or only the divider by itself?
If DC coupled then stage position in the chain may
determine bias current (esp. since LNAs are often simple
common-source FET stages). If you have three stages
and one is dissimilar the difference ought to be
something simple to find. If we had one of those worth-
a-thousand-words things and not just some words of
dubious helpfulness.
Schematic. Post it.
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