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| BJTs being phased out? |
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| tom66:
--- Quote from: NiHaoMike on October 16, 2020, 12:40:34 pm --- --- Quote from: coppice on October 16, 2020, 09:49:03 am ---From my experience with small ICs, I assume the cost of packaging a small discrete, like a 2N7002, now greatly exceeds the cost of the silicon itself. So, the cost of the device is only marginally affected by which transistor is inside. --- End quote --- Perhaps the next step is some sort of simple IC designed to take the place of a small transistor, the value add being built in protection against ESD, overcurrent, and overheating? Such a device, if cheap enough, would work nicely for interfacing sensitive logic to the external world. --- End quote --- Such ICs already exist. MOSFETs with built in pull down resistors, ESD protection etc., or NPN transistors with base resistors on the same die. Then you have things like load control devices that can switch a high side load with overcurrent and slew rate protection, for instance TI TPS22919. Many of them are sub 20 cents in volume which when you consider placement costs of the passive components required to replicate them is not bad at all. |
| schmitt trigger:
A positive development in the small signal bipolar transistor are the built-in bias resistors. Makes using them a breeze. |
| tszaboo:
--- Quote from: NiHaoMike on October 16, 2020, 12:40:34 pm --- --- Quote from: coppice on October 16, 2020, 09:49:03 am ---From my experience with small ICs, I assume the cost of packaging a small discrete, like a 2N7002, now greatly exceeds the cost of the silicon itself. So, the cost of the device is only marginally affected by which transistor is inside. --- End quote --- Perhaps the next step is some sort of simple IC designed to take the place of a small transistor, the value add being built in protection against ESD, overcurrent, and overheating? Such a device, if cheap enough, would work nicely for interfacing sensitive logic to the external world. --- End quote --- What you describe is called "load driver", "relay driver", and MOSFET driver, solid state driver, and so on |
| bsfeechannel:
--- Quote from: Benta on October 14, 2020, 10:26:54 pm ---Almost no major semiconductor manufacturers have them in their portfolio. And the ones that still have them are "pruning" their availability list. --- End quote --- The truth is that JFETs have never enjoyed the widespread use that BJTs or MOSFETs have. This is the 1976 transistor catalog of IBRAPE, a subsidiary of Philips. You can see some audio signal-, power-, horizontal output- and radio signal transistors among them. But the only JFET is the venerable BF245. So the "pruning", if it ever existed in fact, started long ago. What is ironic is that the bipolar transistor was discovered when physicists were trying to build the first FET, but failed. The BJT appeared as an enhancement over the original transistor and provided the ideas to finally create the (J)FET. However, despite the fact that JFETs most closely resemble the behavior of a pentode, by that time the BJT was already established as the semiconductor replacement for tubes. A few years later the MOSFET came up and rendered the JFET further irrelevant as a general purpose solution. Had they succeeded in inventing the JFET before the BJT, who knows how different history would be. In all those years what I've seen JFETs do was to work as LF/RF front ends, RF oscillators, switches for analog signals, electronically controlled resistors and constant current sources or sinks. And some obscure or very specialized applications. My hope is that in 20 year's time baking your own JFET, or any other semiconductor, be as inexpensive as producing your own PCB and you will be able to have it done to your specs for 2 bucks. |
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