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How to de-sensitize the gate voltage in an amplifier ?

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liletian

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Hi Guys
I want to design a amplifier with gain of 5-10, so I choose a signal transistor amplifier(common source). But the output DC point is very sensitive to the DC voltage of gate which is not what I want, is there a better structure to use or how to de-sensitive the gate voltage?I need a stable gain up to 5Mhz which is not hard to get.
Thanks
 

Re: amplifier question

Your amplifier apparently misses a DC negative feedback.
 

Re: amplifier question

yes, but a negative feedback will cause a lot of power assumption, right? I do not want to consume energy. My current new design is using a degenerate common source amplifier, is there some better single structure.
Thanks
 

amplifier question

If circumstances allow it, you should put a capacitor in series with the CS transistors gate - make the amplifier AC coupled. This will block out input DC voltage, you can use whatever biasing structure to set the DC voltage at the gate.
 

Re: amplifier question

the ac frequency is in a range of a few Mhz, so is it easy to ac couple? how large should be the capacitor? I am not very experienced, thanks for your help.
 

Re: amplifier question

you should some how restrict the current that flows through the transistor to have a constant gm, use a current mirror.
 

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