RF Power amplifier stability

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Mabrok

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I have designed class AB Power amplifier for 3.4-3.6 GHz band. When i checked the stability, the amplifier was stable over the entire band (K>1). But for out of band at certain frequencies (0.5 to 1.2 GHz & 3.9 GHz ) is unstable. So, Is this condition will have an effect on the PA's performance?
 

The amplifier may oscillate-not definitely but-.If K<1, the amplifier is conditionally stable so certain load and source impedances may drift it into oscillation.If K<0, the amplifier will probably oscillate..
Adding resistors at input and/or at output may help you or highpass/lowpass filters can also help to reduce the risk.
 
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    Mabrok

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I have added resistor in series and helped in enhancing the stability. but on the other side degraded the gain too much.
 

Mabrok said:
I have added resistor in series and helped in enhancing the stability. but on the other side degraded the gain too much.
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Parallel resistors are used at input/output or both..Consider also highpass/lowpass filter combination.
There are numerous solution for the stability..
 
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