Total harmonic Distortion - Differential Signal - Ltspice

[kjha]

Hi Everyone..

I am trying to get the THD of an amplifier output in LTspice.
I used .four <freq> <signal> spice directive with .tran analysis and I can get the THD of a single ended signal..but i need THD of a differential signal..(LTspice just does not give anything when i try to enter a diff signal..)
does anyone know how to get the THD of a Diff Signal in LTspice??

Thanks in advance..

 

[keith1200rs]

You could just use a VCVS (voltage controlled voltage source) to turn the signal into single ended.

Keith.

 

[kjha]

You could just use a VCVS (voltage controlled voltage source) to turn the signal into single ended.

Keith.

Thanks a lot Keith..

I did that and it seems to work..

btw..1 more question.. the THD on V+ and on V- is high..but that on [(V+) - (V-)] is lower....(LTspice shows a much lower voltage on even order harmonics for [(V+) - (V-)] )...
That's the way it is supposed to be right??

Thanks!

 

[keith1200rs]

I can check if you show a circuit, but yes, it is perfectly possible. Some distortions (e.g. Second harmonic I think) can be cancelled out in complementary outputs.

Keith

 

[srigoa91]

Hello Keith,

Can you tell me how & where can I find the VCVS for differential to single ended conversion? Is it a component in LTSPICE ??

 

[keith1200rs]

VCVS is an E source. It is in LTspice simply as e. It has two inputs and two outputs so is differential in/differential out. If you ground one of the outputs you will effectively make it single ended out.

Keith