[<<][synth][>>][..]Fri Dec 24 00:10:36 EST 2010
One things I got wrong is the use of two current mirrors that take the current from the two differential pair legs and bring it out. See explanation and CA3080 schematic here[1]. The schematic I'm working with is the differential pair with current mirror load [2], and the discrete 4-pole filter [3] (which has the PNP's upside down in the schematic).. So what's the difference? Why the two extra current mirrors? The answer is probably to remove the dependency on the common mode voltage. I.e. if that's high, the differential pair resistors might saturate trying to provide a low output voltage. However, if by design this isn't a problem (as in the 4-pole filter?) the current mirror can be left out. [1] http://www.uni-bonn.de/~uzs159/ota3080.html [2] http://en.wikipedia.org/wiki/Long_tailed_pair#Long-tailed_pair [3] http://www.jhaible.de/tonline_stuff/jh2040.gif
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![[3]](http://www.jhaible.de/tonline_stuff/jh2040.gif){kind=link}