Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

differential amplifier can suppress even order harmonics?

Status
Not open for further replies.
K

katrin

Full Member level 1
Full Member level 1
Joined
Dec 3, 2005
Messages
98
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Visit site
Activity points
2,200
I often read that the fully differential amplifier can suppress even order harmonics,
but I don't really understand why.
Could someone explain it?

thanks
 

Re: differential amplifier can suppress even order harmonics

For any amplifier:
Vo=a0+a1Vi+a2*(Vi^2)+a3*(Vi^3)+a4*(Vi^4)+a5*(Vi^5)+............
where a2,a4,a6,....... are the even harmonics coefficients
while a3,a5,a6,........ are the odd harmonics coefficients
Since the sign of the input will not appear in the even harmonics terms as it is always raised to the power of an even number, thus at the two outputs of the differential amplifier the even harmonics are the same(assuming perfect matching) and thus when the two output are subtracted(differential output) the even harmonics on both sides will cancel each other.
 
  • Like
Reactions: dinos7 and sabbasi

    S

    sabbasi

    Points: 2
    Helpful Answer Positive Rating
    D

    dinos7

    Points: 2
    Helpful Answer Positive Rating
    M

    mvj

    Points: 2
    Helpful Answer Positive Rating
it is cancalling at the output because differential output is Vp-Vn

But if the circuit has any mismatch between the two sides of the differential pair, the even harmonics will show up at the output.
 

Re: differential amplifier can suppress even order harmonics

so, exactly speaking, because of device mismatch, fully differential amplifier cann't completely suppress even order harmonics, just reduce them to a low level.
 

    K

    katrin

    Points: 2
    Helpful Answer Positive Rating
"For any amplifier:
Vo=a0+a1Vi+a2*(Vi^2)+a3*(Vi^3)+a4*(Vi^4)+a5*(Vi^5)+............
where a2,a4,a6,....... are the even harmonics coefficients
while a3,a5,a6,........ are the odd harmonics coefficients "

I really don't know are they true or not.

"Since the sign of the input will not appear in the even harmonics terms as it is always raised to the power of an even number, thus at the two outputs of the differential amplifier the even harmonics are the same(assuming perfect matching) and thus when the two output are subtracted(differential output) the even harmonics on both sides will cancel each other. "

can you explain more please?????
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top