Depletion Mode Switch for Audio or Solid State Relay

Hello Zach,

Sorry I only noticed your post just now. There is a glitch in our notification system. Not your problem. 

I think your question is best answered by our switches and multiplexers group. Ask the question there. I would move this but now that it is late it is not fair to the other group. 

(+) Switches/Multiplexers - EngineerZone

I have personally used switches for audio and we have some really good low distortion switches available. You are mentioning -5V. Many of these switches are all relative to the reference you give it. I have used switches meant for bi-polar designs in a single ended amplifier design by setting up a pseudo ground or just referencing the digital control reference to the negative rail.  This would give me over 40V of range with a part designed for +-20V. 

It would help to get a little more detail as to the signals it will be switching? What is the max signal levels? Is it ground referenced? Since you are asking about -5V I assume it is not. Perhaps show us an example use?

We do have solid state relays as well that are designed for RF work so it is low capacitance. 

Dave T

Hello Zach,

Sorry I only noticed your post just now. There is a glitch in our notification system. Not your problem. 

I think your question is best answered by our switches and multiplexers group. Ask the question there. I would move this but now that it is late it is not fair to the other group. 

(+) Switches/Multiplexers - EngineerZone

I have personally used switches for audio and we have some really good low distortion switches available. You are mentioning -5V. Many of these switches are all relative to the reference you give it. I have used switches meant for bi-polar designs in a single ended amplifier design by setting up a pseudo ground or just referencing the digital control reference to the negative rail.  This would give me over 40V of range with a part designed for +-20V. 

It would help to get a little more detail as to the signals it will be switching? What is the max signal levels? Is it ground referenced? Since you are asking about -5V I assume it is not. Perhaps show us an example use?

We do have solid state relays as well that are designed for RF work so it is low capacitance. 

Dave T

Hey Dave - no worries. Thanks for the answer.

I'm working on a device with my engineers that needs to be able to pass audio when there is no power. We're currently using the MAX97220 as our headphone amp. We have a situation where the headphone amp may be disconnected from the load, in the event that someone is using in-ear monitors and detaches a monitor from the cable while powered. In this case the MAX97220 would have a voltage swing (-5 to +5v in this case) and would potentially damage the FSA515 if we were to use several of them to build our own solid state relay.

I've seen some ADI switches that are rated higher than +-5V but they don't seem to pass audio when unpowered. (i.e. https://www.mouser.com/datasheet/2/256/MAX20327-1393358.pdf)

Max signal level input would be coming from a headphone amp that outputs 5V peak to peak at 32 ohms so we should be in the bounds of the FSA515 which has a max negative swing of -3.3V and max of +5V. (basically a headphone amp that outputs 100mW at 32ohms)

We will essentially be taking that input signal and running the output at unity gain to match the input volume but adding some more signals to it which will be a bit louder/higher output than the unity gain signal.

Hello Zach,

Interesting. I am not sure if I totally understand exactly what you need to do but I do know we have had some call for things like amplifiers/DSPs in headphones that will bypass the input to the output when power is lost so there will still be audio even if batteries are dead. This is for safety systems in things like airplanes. 

I will alert some of the others in the company that deal more with the amplifiers than I do about your question. They will probably need more detail but I will let them ask.

I think they will be back to work tomorrow and they are on the west coast so it will be a bit on the late side for you. Actually in the evening for you.

Dave T 

Sounds good. The requirements are similar to what you described with headphones that will bypass the input to the output when power is lost so there will still be audio when batteries are dead.

We basically need our headphone amp based mixing system to pass audio from an external input directly to the output (bypassing our actively powered DSP and headphone amp in the event that batteries die in our system. We are currently doing it with an electromechanical relay but are looking at minimizing PCB size and height by using some solid state solutions.