analog signal input buffer

[freewing]

In my chip, there is a 200-MHz input signal with an amplitude of 400mV. It's connected to the gate of an NMOS transistor. Is it OK to directly connect the signal pad with the transistor gate? Is it necessary to put some buffer? What kind of buffer would be appropriate? Thanks.

 

[sunking]

pay attention to the matched impedance

 

[suria3]

Hi,

You can directly connect the input signal to the gate of transistor as long you match the 50ohm line transmission which we consider as input matching. In case you want to isolate the signal from loading the input, then you can use the source follower (buffer) before the input stage.

Regards,
Suria

 

[Syukri]

As an addition for above, you can directly link them, but for better consistancy you can try a transmission gate for digital part.

But the size of your chip will be increased.

 

[flushrat]

Be care of the terminal impendance and common mode voltage