On Mon, 27 Jan 2014 11:30:37 -0500, Phil Hobbs
wrote:

On 01/27/2014 11:27 AM, John Larkin wrote:
On Mon, 27 Jan 2014 10:18:27 -0500, Michael Black wrote:

On Mon, 27 Jan 2014, RobertMacy wrote:

This is a simple switched capacitor filter made by National. Would somebody
send me a copy, or at least provide a URL that HAS it!!! and not datasheet or
alldata crap! If AppNote available that too please.

Have you got the part number right? National's first generation filter
like that had some other prefix (I can't remember what, I'd know the minute I
saw it). I'm thinking "MFC" but I don't know why. It didn't start
with National's traditional prefix, "LM". Maybe later they used some other
prefix, but I'd double check.

National's classic switched-cap filter was the MF10, metal-gate CMOS. There was
a later poly-gate version, can't remember the part number.


The LMF100. Nice part if you needed to do anything fancy and low SNR
was okay. I used it to make a SSB mixer once, and it worked great.

Overall, switched-cap filters weren't all that great. OK for some apps, but they
were really noisy, and aliased anything available, including power supply crud.

I once designed a double-conversion superhet FSK modem full of MF10s, for
Reuters' landline newswire service. Sold a few before PCs and the Internet made
the classic newswire thing obsolete.

The clock-tunable thing was pretty convenient for some jobs, especially
back when tight-tolerance capacitors were expensive.


Yeah, the modem did any channel, and any one of three baud rate/bandwidths, with
just dip switches. The older stuff had plug-in LC filters.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation