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Cadence Virtuoso: How to get Common Mode Gain of a basic Differential Amplifier?

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Oscilliscoper

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Hi Everyone, I have a question about how to use the Cadence Virtuoso software. I've never used it prior to yesterday, but I'm required to use it for an assignment and my instructors haven't given the class any training on the software at all.

I have to simulate the behavior and characteristics of the differential amplifier pictured below. The upper half is the differential amplifier, while the lower half is a current mirror. Where VDD = 1.8V, RD = 2.5 kOhms, IREF = 100 uA, Q1 and Q2's W/L = 5um/0.18um, Q3 and Q4's W/L = 10um/0.5um.

After Googling around and watching some YouTube videos I've figured out how to get the DC currents and voltages for a common mode voltage of 1 V. I've also indirectly figured out how to calculate the small signal differential gain from toying around a bit. The results matched my hand calculations, so I figured they must be correct.

**broken link removed**

The part I am now stumped on is this: When the resistors are mismatched by 1%, I have to calculate the common mode gain. This is fairly easy on paper, as we covered this case in class, but I have no idea how to simulate this in the software.

Online searches haven't really turned up anything and there are literally hundreds of options in the Analog Design Environment (ADE) to try everything.

My circuit schematic looks like the following in Virtuoso:

**broken link removed**
 

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