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Quick question on the post, in the paragraph on metal gate transistors there are a couple of advantages listed. The last one says, "Third, metal-gate circuitry
by egsmi 6y ago
Quick question on the post, in the paragraph on metal gate transistors there are a couple of advantages listed. The last one says, "Third, metal-gate circuitry required an additional +12 V power supply."
It's not clear to me why a +12V supply would be an advantage? Did 1974 have their equivalent of ATX supplies so that meant one less rail the PCB needed to generate compared to silicon-transistor designs?
And there is some interesting cut in the ceramic that is exposing the lead frame on the left side of the package in the picture that is showing where the -2.5V bias note was written. Do you know what that is?
- jacobr1 6y agoThat is a disadvantage. > First, silicon-gate transistors were smaller, faster, and more reliable. > Second, silicon-gate chips had a layer of polysilicon wiring in addition to the metal wiring; this made chip layouts about twice as dense.8 > Third, metal-gate circuitry required an additional +12 V power supply. This implies silicon-gate chips DO NOT require the additional power supply.
- kens 6y agoAs jacobr1 pointed out, it's a disadvantage of metal-gate transistors, not an advantage. Silicon-gate transistors are entirely better than metal-gate transistors. (Except now metal-gate transistors are coming back for high performance, using "high-k" metals like hafnium. But these are completely different from 1970s-era metal-gate transistors.) For your other question, the visible metal trace on top of the IC package is a common thing with ceramic packages. I think the purpose was to ground the metal lid of the IC to protect against noise, static, etc.
- egsmi 6y agoOh, I see. I completely misread that paragraph. If the metal strip is on the top of the ceramic and grounded it makes sense that it would be for ESD protection. Especially as they likely did hand assembly of the PCBs.