Bob Cordell Interview: Negative Feedback

Jump to Latest
#45
john curl said:
Bob, as Matti defined it to me, 30 years ago: TIM is a subset of distortions included in DIM. DIM means: 'Dynamic Intermodulation distortion' and includes TIM as well as any other 'dynamically' manifested distortion, such as PIM, etc.
DIM 30 could just as well have been named TIM 30, but I suspect that Matti was trying to create a more inclusive distortion picture than just TIM, which had been pretty well researched by this time, but did not appear to explain 'everything' that appears to be important in amp performance with dynamic signals.
Click to expand...


Thanks for the claification, John. That seems reasonable. It coincides with what I measure when I do a DIM measurement.

Bob
 
#47
PB2 said:
Yes, I got: "Use ".option noopiter" to skip."

Is it safe to skip, I've not used this option?
Click to expand...

Yes, it's safe to skip. My sim does that also. After it fails with this strategy, it should go into the source stepping strategy with a bunch of entries that look like this at the end:

Source Step = 86.9243%
Source Step = 90.2149%
Source Step = 93.5056%
Source Step = 96.7963%
Source Step = 100%
Source stepping succeeded in finding the operating point.

If the source stepping fails, then it starts the sim from an arbitrary set of initial conditions. Sometimes these conditions are so far off that they can cause high frequency ringing such that the time step required to track them becomes too small compared to the time span. That's when you get the "time step too small" message.

Sorry about this guys. 🙁 Further discussion on this should probably be in email, as it's getting off-topic.
 
#53
Re: Re: Re: Re: Re: Re: Perspective on Open Loop Bandwidth Comparisons

andy_c said:


The extent of the common-mode effects in the sim really surprised me a lot.
Click to expand...

Andy ,

thank you for the examples!

This is the reason why I prefer the inverting circuit!

If you try your simple stage in inverting mode you will see that the distortion is even a bit less.

Regards
Heinz!
 
#56
Re: Re: Re: Re: Re: Re: Re: Perspective on Open Loop Bandwidth Comparisons

powerbecker said:


Andy ,

thank you for the examples!

This is the reason why I prefer the inverting circuit!

If you try your simple stage in inverting mode you will see that the distortion is even a bit less.

Regards
Heinz!
Click to expand...

Actually, using a bootstrapped cascode solves that problem; no need to revert to the necessarily noisier inverting configuration.
 
#59
Re: Re: Re: Re: Re: Re: Re: Perspective on Open Loop Bandwidth Comparisons

powerbecker said:
This is the reason why I prefer the inverting circuit!

If you try your simple stage in inverting mode you will see that the distortion is even a bit less.
Click to expand...

Hi Heinz,

Good to see you back!

I suspected that an inverting configuration would also have the same effect. One thing that concerns me about inverting mode is that if the input is open for whatever reason, there's a feedback factor of 1, which could lead to oscillations. This worries me, so I figure non-inverting is a safe solution.

BTW, thanks again for your circuit for biasing the diodes for clipping. You probably noticed it in my file from the other forum.
 
You must log in or register to reply here.
Top Bottom