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Crunching an AC signal

I have a unidirectional AC signal (25MHz square wave, 1V amplitude) that is AC coupled into my circuit and AC coupled to the output. I need a simple way to prevent the signal from passing from input to output. I know I could use a 4066 type analog switch, but I haven't found one the meets my supply, Ron and package type requirements.

Can someone suggest a method of preventing the signal from passing?

My circuit cannot effect the signal when it is not trying to stop it.

Thanks, David

Reply to
David
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Could you crispen up the specs a bit?

  1. What sort of isolation do you need in the off state?
  2. What impedance levels are you using?
  3. Is it okay to short the input?
  4. How much on-state loss is acceptable? ('Zero' is not the right answer.)
  5. What are your supplies, and how much power are you willing to spend?
  6. Would a logic solution work?

This could be anything from a diode switch to a NAND gate, depending on your requirements.

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

50dB

The circuit is a 1uF input coupling cap. that feeds through a 4066 and then to a 1uF output coupling cap. The problem is that the 4066 Ron is too large. I know I can get these with much lower Ron, but I was looking for something much simpler and cheaper.

Yes, after it passes through the coupling cap.

I like zero. ;-) Twenty ohms series R is about as large as the system can withstand.

Power isn't a big deal. Their is a single 12V rail.

Perhaps. I was thinking of a solution that would attach to the signal and not be in its path. I tried an NPN with the collector tied to the signal and the NPN turned on to crunch the signal, but all that did was center the AC signal at 200mV. I can add series resistance to the signal path to allow the NPN to crunch the AC component, but I was hoping to avoid adding any series resistance.

Thanks for the help. David

Reply to
David

I tossed this search string "low r analog switches" to Google and found many things including a Maxim MAX4736 switch. An L pad made with those could give you better than 70 dB isolation.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller
Reply to
joseph2k

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