tag:blogger.com,1999:blog-6264947694886887540.post3536366513333877606..comments2024-03-27T22:51:35.227-07:00Comments on Ken Shirriff's blog: Reverse-engineering a vintage comparator chipKen Shirriffhttp://www.blogger.com/profile/08097301407311055124noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-6264947694886887540.post-39301760507621275192021-04-25T12:59:21.829-07:002021-04-25T12:59:21.829-07:00Duck: You found the mystery resistors :-) I looked...Duck: You found the mystery resistors :-) I looked at them closely and those long resistors appear to be connected at only one end. My guess is that either they decided not to use them, or they are used in a different part. And yes, you're right about the +/- labels.Ken Shirriffhttps://www.blogger.com/profile/08097301407311055124noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-75303118060161122702021-04-25T11:17:21.476-07:002021-04-25T11:17:21.476-07:00It looks like there's a pull-up resistor on th...It looks like there's a pull-up resistor on the in- input and a feedback resistor to the in+ input from what would be out-. Maybe to bias it to a faster response?<br /><br />Also, I think you have in- and in+ swapped for the bottom left comparator. Duckhttps://www.blogger.com/profile/15765131460770984267noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-33418325244970644912021-04-21T07:33:24.144-07:002021-04-21T07:33:24.144-07:00Philips ASICs have names starting with "OQ&qu...Philips ASICs have names starting with "OQ", and they usually come in these ceramic packages. As an example OQ0040 is the heart of the PM 667x frequency counter family.<br />Patricknoreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-79879797607598542342021-04-18T11:06:36.183-07:002021-04-18T11:06:36.183-07:00Very nice write up, brings me back to my early Fai...Very nice write up, brings me back to my early Failure Analysis and Fab support days. The aluminum metalization looks like it has a lot silicon precipitates. Probably 2% to 4% silicon in the metalization. Commonly used in the '70s and early '80s.phase2682https://www.blogger.com/profile/16689941725444987581noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-31884134136344485742021-04-18T05:40:19.929-07:002021-04-18T05:40:19.929-07:00Maybe the reason that only two of the comparators ...Maybe the reason that only two of the comparators have inverted and non-inverted outputs is because that gave the right number of pins for the package that they wanted to use? Inverted outputs could be a bonus, but probably not essential.Toivo Henningssonhttps://www.blogger.com/profile/05599157383718975426noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-11953494767974901632021-04-17T18:43:22.175-07:002021-04-17T18:43:22.175-07:00Steve: you are correct. I missed a resistor when d...Steve: you are correct. I missed a resistor when drawing the schematic. I have updated the schematic with this resistor.Ken Shirriffhttps://www.blogger.com/profile/08097301407311055124noreply@blogger.comtag:blogger.com,1999:blog-6264947694886887540.post-54772271324093296132021-04-17T18:29:44.236-07:002021-04-17T18:29:44.236-07:00Ken,
As a former chip designer I enjoy readin...Ken,<br /><br /> As a former chip designer I enjoy reading your teardowns. Brings back a lot of memories of the "good ol' days". :-)<br /><br /> I think there is a resistor missing in your comparator schematic. It connects the 2 bases and 1 collector in current source 1 to V+. I see it on the layout placed after the schematic.<br /> The schematic of current source 1 doesn't make any sense as originally drawn.<br /><br />Regards, SteveAnonymoushttps://www.blogger.com/profile/00106237425787061583noreply@blogger.com