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HF normally closed switch

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konrad_gom

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Hello,
Does High Frequency Normally Closed Switch exists? It should work up to 3GHz and should have small SMD package.
Explanation what I need:
Relay.png
It should be normally closed switch, which without power supply is closed to one position. So two of them should works as a bypass (with low losses). After power supply comes, switch should switch to second position, to some electronic circuit.
Does such element exists? If yes, please some example.
Regards.
 

GaAs FETs are normally closed (depletion mode JFETs) switches with very good RF poperties, but there's no normally open switch available in this technology. Look for devices from Hittite (now adi) or Skyworksinc.
 

FvM said:
GaAs FETs are normally closed (depletion mode JFETs) switches with very good RF poperties, but there's no normally open switch available in this technology. Look for devices from Hittite (now adi) or Skyworksinc.
Click to expand...
Normally open I do not need. Thx, I will look for it.

- - - Updated - - -

As I saw, there are only ON-OFF switches. But this what I want I don't see (without power supply normally closed in one position, after power supply goes to the second position).

- - - Updated - - -

Looks like I need 1 form C relay: AD4C113 configured in this way: Converting-1-Form-A-1-Form-B-Relay-into-1-Form-C-Relay

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Or not... AD4C113 is not designed for high frequencies.

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This one TE HF3 could be helpful, am I right?
But package is much too big.
 

FvM said:
GaAs FETs are normally closed (depletion mode JFETs) switches with very good RF poperties, but there's no normally open switch available in this technology. Look for devices from Hittite (now adi) or Skyworksinc.
Click to expand...

I think in order to use a GaAs FET switch in his application, you would need to find a SPDT with only series branches, and no shunt branch. Alternatively, you can just use a GaAs FET, but then you would need to provide your own negative voltage...


regards,
Aaron
 

A popular GaAs switch configuration is SPDT, mostly used as Rx/Tx switch. They are comprised of two GaAs FETs with a common node and have no shunt switch. They can be e.g. parallel connected if you use a different bias scheme.
 

FvM said:
A popular GaAs switch configuration is SPDT, mostly used as Rx/Tx switch. They are comprised of two GaAs FETs with a common node and have no shunt switch. They can be e.g. parallel connected if you use a different bias scheme.
Click to expand...

Actually, that doesn't really meet the requirements in his original post. He only wants one of the branches to be normally ON...He needs two different switches, one normally ON, and one normally OFF...

Aaron
 

Yes, I already mentioned that supplyless NO isn't possible with GaAs.
 

FvM said:
A popular GaAs switch configuration is SPDT, mostly used as Rx/Tx switch. They are comprised of two GaAs FETs with a common node and have no shunt switch. They can be e.g. parallel connected if you use a different bias scheme.
Click to expand...

Agreed, a SPDT could be used as an SPST by connecting the switches in parallel (or just using one branch). But my impression is that the vast majority of these do include shunt switches on at least one branch.
 

Simple SPDT switches are also in use, e.g. AS169-73. Switches with shunt paths, either "reflective" or "absorptive" type are used for higher isolation requirements.
 

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