Frank Palazzolo wrote:
I built my kit to do TTL-serial only, and I don't plan to use real RS-232 voltage levels.
Q1 and Q4 (on the Z80MC Front Panel) are only needed for RS-232 serial. So they can be left out. :-)
Another alternative would be to find a compatible N-channel and
P-channel FET in a TO-92 package, which would be ok with the maximum
voltages, and then try to orient the part to that footprint.
An N-channel MOSFET (like a 2N7000 or BS170) might work for Q2 and Q3. Their base (gate) is pulled either high or low (so never left floating).
The base of Q5 is driven by capacitor C5; so you need the base resistors to work. A P-channel MOSFET (BS250) might work if you added a gate-source resistor to insure that it turned it off. Or, you could leave it off -- without it, you can't reset the Z80 with the DTR line from the serial port.
For an active part, it seems like you could find a match in a surface mount package, if you're willing to solder that to the top (or bottom, depending on the pinout).
Right; there are lots of surface-mount alternatives. But watch the pinouts!
Lee Hart
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A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
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Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Lee Hart