zychang
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Posts: 13
Ireland
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Thanks for your comments, guys.
Ok, I'm trying to describe it in more detail. What I'm designing is a multiply-by-2 circuit. As it is bit like the 1.5bit stage in pipline ADC, a positive reference and a negative reference voltage are needed. I can think of two ways of generating these voltages: one is to build a differential reference voltage, like the one mentioned in Razavi's book, so that a negative reference voltage can be realized by cross-connect the capacitors, just like you said in your post Paul. But I found some difficulties in designing the differentianl reference voltage circuit, so I just moved to the second approach(maybe not commonly used by people around but this is the way I can think of since I just started in this area), which is to build two single-end reference voltages. Now, I have no problem building the positive one, but I just have no idea how to realize the negative one. I don't know if the cross-connecting thing is still working here. Also, I have found some thesis on pipeline ADC from the websit of P.Gray's group in UC Berckley, some of them seem to use capacitors array to provide the reference voltage which is a quite different idea from mine. So, if you can give me some advice or reference or what people normally do in this topic, I will very appreciate it.
thanks again.
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