FM IF strip ICs

Philips SA636. Just don't use the mixer.

Thanks,

Frank

What's wrong with it? Too weak?

Cheers,

Phil HObbs

He probably means "just use the IF section". Though I doubt if the 636 would be much cheaper than the 605. The 615 might be worth to look for too. Same as 605 with somewhat lesser specs.

Joop

The OP might also try the NEC upc3217 / 18

No RSSI, but 50-55 dB on the ACG. I use it in DSP radios as the preamp before the ADC.

Frank Raffaeli

Thanks for the steer. One fairly weird thing about these: they're much noisier for high gains (NF = 13 dB @ 23 dB gain, NF = 6 dB @ 4 dB gain). I'd expect them to be quieter at high gains, like every other AGC amp I've ever seen. Are there parallel signal paths or something? I can't think how you'd make a single-path circuit do that. Weird.

Cheers,

Phil Hobbs

We are using the SA605 right now and like it so far. There are good application notes for it, but it is about 10 years old so I think no current support from Phillips. We are using it with two of the narrowest ceramic filters from Murata (CFWLA455KJFA - available from Mouser). We are tapping right off the limiter output, but it is high output impedence, so be careful of that (different loads affect the RSSI reading!). No evalauation boards exist, good layout is important.

Another options are the chips from New Japan Radio Company. Search under "NJM" in Digikey. Samples online are possible from manufacturer, but take a few weeks to get.

BenL

Analog Devices AD608? Paul Mathews