Author Topic: Finding the right analogue switch?  (Read 941 times)

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Offline dzsekiTopic starter

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Finding the right analogue switch?
« on: June 06, 2019, 10:35:30 am »
I’m in need for an analog switch (SPDT, or SPST) for switching wide bandwidth analog signals, the signal is bipolar, but not symmetrically, ie. varies between -100mV and say +1V.
I am tempted to use single supply switches as well either as-is, or perhaps shift the GND pin to -0.6V (by a single diode), and I may translate the logic levels accordingly (if it is needed at all).
-Because the source impedance is 75 Ohm so the switch should have low (on) input capacitance: <10pF
-The on resistance should be as low as possible:  <50 Ohm
-Switching speed is not critical:  <100ns
-Bandwidth: >500MHz

Regarding the bandwidth, I want my bandwidth at the output of the switch, I expect the load on the switch output to be 1M Ohm||4pF worst case, hence my requirement on the low resistance.

I have been looking at these sofar:
-ADG1233: it falis at the low on resistance requirement (>120 Ohm), but should be OK.
-TS12A44514: it fails in low input capacitance criteria (>19pF)
-TMUX154E: it would meet all criteria, but this switch is not meant to used with analog signals, so I am hesitnant on this model yet...
HP 1720A scope with HP 1120A probe, EMG 12563 pulse generator, EMG 1257 function generator, EMG 1172B signal generator, MEV TR-1660C bench multimeter
 

Offline mikerj

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Re: Finding the right analogue switch?
« Reply #1 on: June 06, 2019, 11:19:53 am »
-TMUX154E: it would meet all criteria, but this switch is not meant to used with analog signals, so I am hesitnant on this model yet...

Why do you say it's not designed for analog signals? Looks like a high bandwidth analog switch to me.
 

Offline dzsekiTopic starter

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Re: Finding the right analogue switch?
« Reply #2 on: June 06, 2019, 11:40:51 am »
Well, they simply don’t mention analog signals in the datasheet at all, nor they give distortion specs, while the other mentioned datasheets are containing these, so I got suspicious, that’s all.
HP 1720A scope with HP 1120A probe, EMG 12563 pulse generator, EMG 1257 function generator, EMG 1172B signal generator, MEV TR-1660C bench multimeter
 

Online SiliconWizard

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Re: Finding the right analogue switch?
« Reply #3 on: June 06, 2019, 04:52:25 pm »
Would the ADG633 fit your requirements?
 

Offline Benta

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Re: Finding the right analogue switch?
« Reply #4 on: June 06, 2019, 06:55:49 pm »
Vishay DG417/418/419.


 

Offline dzsekiTopic starter

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Re: Finding the right analogue switch?
« Reply #5 on: June 06, 2019, 08:06:28 pm »
Thank you.
Yes, I was already looking at the ADG633 and it meets all my criteria, but barely, I'd be happy to find something better.
The DG417/8/9 has way too much input capacitance (30pF)
HP 1720A scope with HP 1120A probe, EMG 12563 pulse generator, EMG 1257 function generator, EMG 1172B signal generator, MEV TR-1660C bench multimeter
 

Offline OwO

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Re: Finding the right analogue switch?
« Reply #6 on: June 07, 2019, 04:21:42 am »
You might want to characterize some CMOS or GaAs RF switches, especially the ones that say "no decoupling caps needed on all ports", because from my tests these all can work down to DC. They are designed for signals centered on 0V, so should be able to pass signals between -5V and +5V if the switch is rated for 0.5W (27dBm) for example. The MXD8625 might be able to do what you want, the only spec it doesn't meet is the switching time (2us instead of 100ns).
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