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Author Topic: [help] how to switch a current source?  (Read 1161 times)
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DreamCat
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« on: August 12, 2011, 04:00:22 16:00 »

I want to generate a triangle wave, and I know that use a const current source to charge a capacitor can get a good linearity of the waveform.

but, when I use very high frequency square wave to switch a CCS cirruit, the current of the CCS has glitch on the rising-edge and falling-edge of the square wave.

it seems that it is caused by the Miller effect. but I have no idea to cancel it.

Anybody know how to resolve this problem?
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TomJackson69
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« Reply #1 on: August 12, 2011, 05:44:02 17:44 »

DreamCat,

This link may help: http://www.edaboard.com/thread180868.html?vm=r

The topic is: how to remove the glitches

Tom
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Con Rong Chau Tien
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« Reply #2 on: August 12, 2011, 11:03:06 23:03 »

You need a stiffer current source. Have you looked at cascoding it?

The other option is to use it as the tail of a diff amp switch - one side goes to your cap, the other goes to an equivalent impedance.  Draws more power, but glitching is close to zero.

Mother Nature is a cruel whore - she gives nothing you want for free.
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DreamCat
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« Reply #3 on: August 13, 2011, 01:59:48 13:59 »

I'm using a improve current source :
here: http://en.wikipedia.org/wiki/Wilson_current_source#Further_improvement

let me think again...
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