[sdiy] Voltage vs current, was Low voltage synthesis?

Brian Willoughby brianw at audiobanshee.com
Wed Jan 19 01:03:13 CET 2022


I hope I'm replying to the correct thread - this subject seems to have split into two or more threads.

Some of the reasons that chip designers think in terms of current rather than voltage:

1) BJT are current-controlled current sources.

Sure, you can use resistors on the input and output to change these currents into voltages, but:

2) Resistors are *way* more expensive inside a chip than they are on a board. Thus, chip designers are more likely to create a constant current source rather than a resistance, again pushing them towards thinking in terms of currents.

3) I think that FET are voltage-controlled current sources, but maybe that's not the most precise way to describe them. I know less about FET chip design than BJT chip design. Of course, the venerated TL07x and TL08x op-amps are JFET inputs, making them voltage-controlled on the inputs, but op-amps ideally have no current flowing on the inputs. Probably the entire rest of the op-amp circuit is current rather than voltage.

Brian



Am 14.01.2022 um 05:10 schrieb Paul Perry via Synth-diy <synth-diy at synth-diy.org>:
> I'm not an EE, but one thing I have noticed is that the people who design the chips think in terms of current, and the people (like me) who use them, are likelier to think in terms of voltage. Not that it matters, since V=IR. Probably base amateurs like myself think of voltage because it is easier to see on scopes and meters.





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