Electronic – How did bipolar IC density compare to MOS ICs

bipolarcmoshistoryintegrated-circuit

Historically, how did the density of bipolar (e.g. TTL) chips compare with MOS? How complex could bipolar ICs get before they hit limits? Does anyone have a Moore's law-style graph for bipolar technology?

Edit: A specific number I'd like to know is the most transistors or gates implemented on a bipolar IC.

Background, and what I've found so far:

I'm looking at the TTL 74181 ALU chip (1970, 75 logic gates), which was a fairly advanced bipolar chip for its time. At the time, MOS was somewhat ahead in density with thousands of transistors on a chip. But now MOS ICs can have billions of transistors but bipolar is nowhere near that. That got me wondering at what point did TTL (or other bipolar technologies) stop scaling?

I came across Integrated Injection Logic (I2L), a bipolar technology that was supposed to provide MOS-like density. The TI SPB9900 microprocessor (1976) used I2L and had 6034 gates, which surprisingly is more than MOS microprocessors from 1976. I haven't heard much about I2L, so did it die out?

In 1986 there was the MBM10494 64K bipolar ECL RAM, versus 256K MOS DRAM, so bipolar was still fairly close. I haven't been able to find larger bipolar RAMs, so I suspect that's about the limit. Was the limiting factor power consumption, manufacturing, economics, or something else?

Best Answer

CMOS eclipsed bipolar technologies because of the power savings. All bipolar logic draws substantial current when idle and, since at least the 1990s, it becomes impossible to get the heat out of the chip long before you run out of space for transistors.