24 Oct
2016
24 Oct
'16
9:01 a.m.
On Oct 23, 2016, at 2:50 PM, shadoooo <shadoooo at
gmail.com> wrote:
...
The idea of using bare transistors seems to me too much simple.
Not that it couldn't work, but it would be almost impossible to satisfy all
the specifications of the bus in this way... unless you use a more complex
circuit with precise current sources and resistors to grant correct voltage
biases, impedances and slew rates, which in the end is a logic integrated
circuit.
I don't know about the receiver part, but I'd expect that the drivers could very
easily be done with a simple transistor circuit. After all, that's what an open
collector (or open drain) driver is, in essence. And the spec is quite straightforward,
it demands an adequate current sinking capacity which is easy to meet. As for slew rates,
unless you have antique transistors, that's not going to be an issue given that you
meet the current sink spec; the slew rate of an OC circuit is determined by the system
capacitance and the sink current of the driver.
Some fiddling with SPICE should yield simple answers here.
paul