The Designer's Guide Community Forum - current-controlled current source in Spectre

ethan Community Member Offline Posts: 35	current-controlled current source in Spectre Jul 5^th, 2006, 1:17pm Dear everybody, I am wondering how I can use "cccs" from analoglib in Cadence to build an ideal differential current amplifier. The cccs is two-port instance, no like vccs and vcvs, which are 4-port instances. Which properties should I specify besides the " current gain"? Many thanks.
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ACWWong

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Re: current-controlled current source in Spectre
Reply #1 - Jul 6^th, 2006, 2:25am

the cccs needs a probe to be set before it can produce a current which equals current_gain*current_in_the_probe.

The probe is set in the "Name of Voltage Source" field to a voltage source you are using to monitor the reference current.

So if you put a instance V0 (a vdc @0V) between a differentail input, you can use the cccs to produce a current which is X time greater.

hope this answers your query.

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ethan

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Re: current-controlled current source in Spectre
Reply #2 - Jul 6^th, 2006, 1:11pm

ACWWong wrote on Jul 6^th, 2006, 2:25am:

the cccs needs a probe to be set before it can produce a current which equals current_gain*current_in_the_probe.

The probe is set in the "Name of Voltage Source" field to a voltage source you are using to monitor the reference current.

So if you put a instance V0 (a vdc @0V) between a differentail input, you can use the cccs to produce a current which is X time greater.

hope this answers your query.

Hi ACWWong,

Appreciate your help. Today I tried to build one according to your instruction (attached here). I don't know whether it is correct (most likely no?).

According to the schematic, if I want to sense the difference between the two constant current sources ( two sine waves with 180degree phase shift), I connect on vdc (dc=0v, instance=V1) in between and specify two cccs with vref=V1. But I feel I still miss something here.

In cccs properties, there is "Type of source", which has several options: cccs, and, nand, or and nor. I guess I should select "cccs" option. But how about the other three options? When I click one of the other three options, I find I need to specify the index of the probes.

What I would like to know is that whether I really need two cccs to build an ideal differential current amplifier ? Or I need one cccs enough with several probes selection?

Thank you for your time and help.

ethan

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ideal_differential_opamp.jpg

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ACWWong Community Fellow Offline Posts: 539 Oxford, UK	Re: current-controlled current source in Spectre Reply #3 - Jul 7^th, 2006, 1:39am No your schematic is wrong, you should not connect the PLUS terminals of the cccs to the inputs !. Also you could also only use one cccs, as the vdc probe will measure the differential current. The following schematic works, and should help you understand the usage of cccs.
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西楼 New Member Offline Posts: 4	Re: current-controlled current source in Spectre Reply #4 - Aug 31^st, 2010, 6:25am Excellent,I have learned a lot from your reply.And I find that vdc=0 acts like a probe which can know the quantity of current flowing through it.
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