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seahs Junior Member Offline Posts: 16	Build ideal fully differential amplifier using vcvs Mar 09^th, 2009, 7:13am I saw this one on jacob's circuit design, layout and simulation(pg 841). It is using spice. While I implemented it in sprectre. It always showed vcvs had shorted output( as shown in the graph). I simulated it anway and it didn't work. does anybody know what the problem is?
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: Build ideal fully differential amplifier using vcvs Reply #1 - Mar 9^th, 2009, 8:16am hi, i don't know about cadence,but i think the problem is you have not specified the common mode voltage(you have to put separate common mode voltage source). Thanks, Rajasekhar.
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boe Community Fellow Offline Posts: 615	Re: Build ideal fully differential amplifier using vcvs Reply #2 - Mar 9^th, 2009, 8:26am Seahs, in your schematic, both sources connect to the same nets (according to net names shown); I suggest you remove net vcm and redraw it. BOE
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seahs

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Re: Build ideal fully differential amplifier using vcvs
Reply #3 - Mar 9^th, 2009, 10:08am

raja.cedt wrote on Mar 9^th, 2009, 8:16am:

hi,
� �i don't know about cadence,but i think the problem is you have not specified the �common mode voltage(you have to put separate common mode voltage source).

Thanks,
Rajasekhar.

Thanks for your reply. Actually I had already specified common node voltage.
I also tried seperating them but it did not work. I think it is not a problem whether to seperate them or not. As I saw they are connected together in the jacob text book in spice.

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seahs Junior Member Offline Posts: 16	Re: Build ideal fully differential amplifier using vcvs Reply #4 - Mar 9^th, 2009, 10:48am I changed the vcvs_ahdl from andlLib to vcvs from analogLib, the error message disappeared. But this vcvs has lots of parameters to fill. I filled some of them and it seems still not work.
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Andrew Beckett

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Re: Build ideal fully differential amplifier using vcvs
Reply #5 - Mar 9^th, 2009, 2:54pm

The key problem is (as was said earlier) that it appears that both of the vcvs are connected between vout_p and vout_n . It's not obvious from the schematic snippet why that is. Perhaps you could upload a simple (small) database in (say) tar.gz format with that part of the circuit, so one of us could take a look.

I don't think you need to specify a delay on vcvs - the gain should be sufficient.

Regards,

Andrew.

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Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: Build ideal fully differential amplifier using vcvs Reply #6 - Mar 11^th, 2009, 12:24pm Are vout_p and vout_n netnames, or the pin names of the vcvs?
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holddreams Junior Member Offline Posts: 19	Re: Build ideal fully differential amplifier using vcvs Reply #7 - Mar 17^th, 2009, 8:26am Have you simulated the circuits successfully? You can try the VCVS in the attatchment.
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