EMRFD Message Archive 13905

Message Date From Subject
13905 2017-05-25 17:01:37 vk3hn SA630 RF switch for bandpass filter selection


I have sketched out a PCB for switching a bunch of band-specific BPFs for a homebrew receiver project.  I am intending to put a decent quality Omron surface mount relay at each end of each BPF.  Conventional stuff.  No DC wetting but I don't think I will use this receiver long enough for that to be a problem.     

Last night I remembered I had a strip of SA630Ds and wondered if anyone has used these RF switches in amateur homebrew projects instead of solid state or relay switching.   The datasheet is here: 


They seem like a good option for small signal switching around receiver RF and IF stages. And they are dirt cheap at 10c a piece.  Any opinions or experience?  

73 from Paul VK3HN. 


Summary from SA630D NXP datasheet:

1. General description 

The SA630 is a wideband RF switch fabricated in BiCMOS technology and incorporating on-chip CMOS/TTL compatible drivers. Its primary function is to switch signals in the frequency range DC to 1 GHz from one 50 ohm channel to another. The switch is activated by a CMOS/TTL compatible signal applied to the enable channel 1 pin (ENCH1). The extremely low current consumption makes the SA630 ideal for portable applications. The excellent isolation and low loss makes this device a suitable replacement for PIN diodes. The SA630 is available in an 8-pin SO (surface-mounted miniature) package. 

2. Features and benefits 

 Wideband (DC to 1 GHz) 

 Low through loss (1 dB typical at 200 MHz) 

 Unused input is terminated internally in 50 ohms 

 Excellent overload capability (1 dB gain compression point +18 dBm at 300 MHz) 

 Low DC power (170 uA from 5 V supply) 

 Fast switching (20 ns typical) 

 Good isolation (off channel isolation 60 dB at 100 MHz) 

 Low distortion (IP3 intercept +33 dBm) 

 Good 50 ohm match (return loss 18 dB at 400 MHz) 

 Full ESD protection 

 Bidirectional operation 

3. Applications 

 Digital transceiver front-end switch 

 Antenna switch 

 Filter selection 

 Video switch 

 FSK transmitter

13906 2017-05-25 17:21:21 Dave Re: SA630 RF switch for bandpass filter selection
  Looks like those should work well.  On the BPF board   that I sell, I use the 74FST3251 analog mux.  I see about 0.5 dB of loss through the  switch.  The surface mount inductors add 3 to 5dB more.  Each board holds 6 filters and use 2 of the 74FST3251 chips.

Dave - WB6DHW

13907 2017-05-25 18:18:40 Harold Smith Re: SA630 RF switch for bandpass filter selection
They look good, but where the heck are you finding them at a dime apiece?  Digikey and Mouser have them at upwards of $3 each.

de KE6TI, Harold

13914 2017-05-26 02:54:14 bellettau Re: SA630 RF switch for bandpass filter selection
Available as 'disposals' in VK.


13930 2017-05-28 16:49:32 vk3hn Re: SA630 RF switch for bandpass filter selection
Dave (WB6DHW)

I had a look at your website and kits, the BPF module    looks good, nice and compact.  Your use of two 74FST325s is neater than a pair of SA630Ds per filter, 2 chips instead of 12, it being a 1 of 8 switch is perfect for this application.   

I can't get the 74FST3251 but element14 (Farnell) has:

SN74CBT3251D - 

FET Multiplexer / Demultiplexer, CBT Family, 1 Channels, 8:1, 4 V to 5.5 V, SOIC-16

Thanks for the tip.  Paul VK3HN. 

13931 2017-05-28 17:46:07 Dave Re: SA630 RF switch for bandpass filter selection
  The SN74CBT3251 are the same thing, just a different manufacturer.

Dave - WB6DHW