Current Mirror

[stinius]

Hi Guys and happy new year to all.

The last few days I have been designing current mirror circuits.
I ended up with a design that I haven’t seen before so I searched the web to see if I could find something similar, but I didn’t.
The interesting thing was that I found this patent (US 20090315618) by Sanyo published Dec. 24th 2009.
I’m really surprised that they are claiming a patent on this circuit; how small change can you actually do to a well known building block and claim a patent?

Cheers
stinius

[darkfenriz]

LOL, seems like you can patent anything today

[jcx]

looks like mosfet feedback/buffer Q driving bjt ccm is prior art here - my post from 2005, beating their priority date by a year (not that I thought the circuit was all that original)

Originally Posted by jcx

A somewhat symmetric mirror+vas with low base current error:



(note that gif and png are much better for line drawings than .jpg)

there are simpler approximations to an ideal diff pair but I think this works and has correct Vin scale factor

usual LtSpice source – just rename without .txt

[Bob Cordell]

Originally Posted by stinius

Hi Guys and happy new year to all.

The last few days I have been designing current mirror circuits.
I ended up with a design that I haven’t seen before so I searched the web to see if I could find something similar, but I didn’t.
The interesting thing was that I found this patent (US 20090315618) by Sanyo published Dec. 24th 2009.
I’m really surprised that they are claiming a patent on this circuit; how small change can you actually do to a well known building block and claim a patent?

Cheers
stinius

Hi Stinius,

This is unbelievable. They are just substituting a MOSFET for the "helper" transistor that has been in common use for decades.

Cheers,
Bob

[scott wurcer]

Wow, I don't get it. Why even bother spending the money?

[Joachim Gerhard]

Look at this. I worked on this over new years. Please do not build it. It´s a concept. I have seen the "helper" transistor in a book from John Linsley Hood "The Art of Linear Electronics" first published in 1993 in the reprint of 2006 by Audio Amateur on page 93 under the name "Improved Current Mirror" and it must have existed for a long time.
i claim the book : "A more sophisticated dircrete component current mirror.... where Q3 is added as a buffer to remove the base current of Q1 and Q2 from the current draw from the input....."

[wahab]

Originally Posted by Bob Cordell

Hi Stinius,

This is unbelievable. They are just substituting a MOSFET for the "helper" transistor that has been in common use for decades.

Cheers,
Bob

hi bob,
not even, as in current mirrors using mosfets, the helper is mosfet..
what they seems to patent is the use of boths bjts and mosfets in
a same current mirror..
anyway, it s easier to patent something that already exists...

regards,

[godfrey]

Extremely annoying!

Originally Posted by scott wurcer

Wow, I don't get it. Why even bother spending the money?

So that e.g. jcx can't implement his own circuit (which precedes Sanyo's) without paying them royalties (unless he can afford to challenge the patent in court). mutter mutter mutter

Stinius - I presume you came up with something a little more interesting.
Care to share, or are you also thinking of a patent?

[tiefbassuebertr]

To the same subject there are additional this thread:
Hashimoto's New Current Mirror - Sanyo's patent present prompt on Christmas Eve 2009
I have contact SY to summarize these two threads

[wahab]

Originally Posted by tiefbassuebertr

To the same subject there are additional this thread:
Hashimoto's New Current Mirror - Sanyo's patent present prompt on Christmas Eve 2009
I have contact SY to summarize these two threads

tiefbassuebertr, as i told you in your thread, the discussion about
this patent is already patented at DIY audio...in this very thread..