| Author |
Message |
xusoso
Joined: 18 Aug 2004
Posts: 90
Helped: 2
|
 30 Sep 2004 8:09 can anyone explain this circuit for me |
|
|
|
thanks advance
|
|
| Back to top |
|
 |
Fom
Joined: 10 Mar 2004
Posts: 758
Helped: 56
Location: Taiwan
|
| 30 Sep 2004 10:18 Re: can anyone explain this circuit for me |
|
|
|
Next time use GIF file less than 100K instead of JPG file. Nobody want to loss his valuable points.
First time I thought it is a differential comparator. It should compare voltage difference A-B and C-D. But I was confused by R1C1 and R2C2 frequency compensation. If it is comparator it doesn't need any frequency compensation, because never works with feedback. Another thing: it seems to me it is something wrong with this circuit. Where did you get that? As to me if disconnect gate of M21 from drain of M22 and connect to gate of M11 it looks much better.
|
|
| Back to top |
|
|
radiohead
Joined: 13 May 2004
Posts: 326
Helped: 21
Location: Heart of Europe
|
| 30 Sep 2004 23:49 Re: can anyone explain this circuit for me |
|
|
|
| To my humble opinion I would not say it is a comparator, but an amplifier. The differential stages convert input voltage A-B and C-D to currents. These are substracted, so we get A-B-C+D. Finally the last stage is a transimpedance amplifier. It converts current back to voltage, with a factor 1k namely. The large cap is there to prevent influence of resistor on biasing.
|
|
| Back to top |
|
|
Fom
Joined: 10 Mar 2004
Posts: 758
Helped: 56
Location: Taiwan
|
| 01 Oct 2004 14:40 Re: can anyone explain this circuit for me |
|
|
|
| But it seems to me if gate of M21 is connected to drain of M22 transistor M29 never will be switched off. So I prefer connection like I mentioned above.
|
|
| Back to top |
|
|
ramone
Joined: 05 Oct 2003
Posts: 60
Location: Patras University
|
| 01 Oct 2004 14:51 Re: can anyone explain this circuit for me |
|
|
|
| the way i see it FOM seems to be right... allthough it also looks to me as an Amplifier... the amplifying stages look clear and the same seems for the noise rejection... well i can't be sure but that's my opinion...
|
|
| Back to top |
|
|
sunking
Joined: 25 May 2004
Posts: 914
Helped: 46
|
| 02 Oct 2004 8:09 Re: can anyone explain this circuit for me |
|
|
|
| It looks an amplifer mostly. And more, it seems a high frequency amplifer using dump factor comp. (DFC) amplifier
|
|
| Back to top |
|
|
tennad
Joined: 15 Mar 2003
Posts: 15
|
| 02 Oct 2004 13:40 can anyone explain this circuit for me |
|
|
|
| I think this is a amplifer,AB input and CD input have difference property.
|
|
| Back to top |
|
|
sda
Joined: 22 Apr 2002
Posts: 117
Location: Greece
|
| 02 Oct 2004 14:30 Re: can anyone explain this circuit for me |
|
|
|
@xusoso
If you have posted the circuit as a quiz here, OK
If not, at least give a breif explanation of where you got it from, or what its supposed to do, as everyone here, isn't in the game of guessing or imagining the designers intentions.
Cheers
sda
|
|
| Back to top |
|
|
terryssw
Joined: 18 Apr 2004
Posts: 176
Helped: 14
|
| 03 Oct 2004 6:59 Re: can anyone explain this circuit for me |
|
|
|
| It seems to be a differential difference amplifier, but are you sure this circuit works? It is strange that why differential pair A-B and C-D not symmetric, and also why the current mirror in A-side connected to nothing?
|
|
| Back to top |
|
|
hanjiemy
Joined: 11 Jun 2004
Posts: 54
|
| 10 Oct 2004 9:50 can anyone explain this circuit for me |
|
|
|
| yes, i agree with terryssw. Is there no output of AB part?
|
|
| Back to top |
|
|
xusoso
Joined: 18 Aug 2004
Posts: 90
Helped: 2
|
| 10 Oct 2004 11:10 Re: can anyone explain this circuit for me |
|
|
|
what is DFC amplifier, can you explain more?
thanks
|
|
| Back to top |
|
|
ME
Joined: 14 Mar 2002
Posts: 1771
Helped: 11
|
| 10 Oct 2004 11:14 Re: can anyone explain this circuit for me |
|
|
|
| Fom wrote: |
| Next time use GIF file less than 100K instead of JPG file. Nobody want to loss his valuable points. |
Actually it is much better to use .PNG instead of .GIF or .JPG.
PNG is smaller than GIF and you don't have ay quality loss as you have with GIF.
|
|
| Back to top |
|
|
xusoso
Joined: 18 Aug 2004
Posts: 90
Helped: 2
|
| 10 Oct 2004 12:21 can anyone explain this circuit for me |
|
|
|
| this circuit is a part of DAC chip. we extract it using eda software.
|
|
| Back to top |
|
|
layes
Joined: 27 Sep 2004
Posts: 57
Helped: 2
|
| 11 Oct 2004 5:08 Re: can anyone explain this circuit for me |
|
|
|
cd input of a diff_out two stage amp
ab control curernt (perhaps)used as CMFB
|
|
| Back to top |
|
|
ue
Joined: 22 Jan 2004
Posts: 32
Helped: 2
|
| 11 Oct 2004 8:11 Re: can anyone explain this circuit for me |
|
|
|
as it sems to me circuti has four part
a-b diff pair
c-d diff pair.
buffer stage 1
buffer stage 2 - provide output
operation :
*a-b* provide output and it is provided to *bias c-d* pair's load and thus
biasing, magnitude of output provided by c-d stage.
probably reason for having *buffer stage 1* is not much clear to me but i suppose it is for freq compensation and making pair of load in *c-d circuit* identical.
purpose of *bufferstage 2* is to boost the current signal received from
*c-d stage*
--
considering this is circuit part of dac - probaly
(a-b) is less significant bit
(c-b) is more significant bit
and a and c are providing reference ground for the bit b and d.
/ue
|
|
| Back to top |
|
|
xusoso
Joined: 18 Aug 2004
Posts: 90
Helped: 2
|
| 11 Oct 2004 13:10 Re: can anyone explain this circuit for me |
|
|
|
dear all
there is a mistake in the circuit.
the gate of m21 should connect to the gate of m18,not to the drain of m22
so this is the cmfb circuit. the input A is connected to a ref voltage, and input B is a feedback of common mode of output.
sorry for my mistake, and thank all of you.
|
|
| Back to top |
|
|
