18 Sep
2013
18 Sep
'13
11:13 a.m.
On Sep 18, 2013, at 1:38 PM, Pete Turnbull <pete at dunnington.plus.com> wrote:
I meant a 7408 (non-OC) as an AND gate to drive a separate transistor
to make the open-collector gate. It's not a great solution.
There are, but you'll likely have the same problem; they're not usually
designed to drive/sink that much current. A dual FET in a tiny SMD
package will essentially be a NAND gate if you wire one source to the
other drain. If you have time to spin a tiny PCB, that's probably an
ideal solution. I can point to some good choices if you'd like, though
you'd have to verify that they're available quickly with your preferred
distributor.
- Dave
On 18/09/2013 17:34, David Riley wrote:
That could work, as long as you're not causing fanout problems for
the devices driving the 7401.
On Sep 18, 2013, at 8:45 AM, Pete Turnbull
<peter.turnbull at york.ac.uk> wrote:
Well, I want something that fits an existing IC socket, and for the
moment I'm thinking if one 7401 doesn't have the oomph, piggyback a
second. Anyone got practical experience of substituting
for an 8881?
My best solution has been
to just use discrete SMD FETs on the output side The problem
is that the 7408 has a different pinout than the 7401/8881 (the gates are
reversed).
I think you mean a 7438 -- right drive capacity, wrong layout. Your other
option would be making NAND gates with individual transistors:
I've not really looked, but aren't there any single SMD NAND gates that
would fit four to a small piece of real estate?