I have protected an RF receiver antenna input using an SCR-based ESD clamp before. Like these devices: http://www.littelfuse.com/products/TVS+Diode+Arrays/General+Purpose+ESD+Pro= tection/SP725.html or, even lower voltage: http://www.littelfuse.com/products/TVS+Diode+Arrays/Lightning+Surge+Protect= ion/SP03-3.3/SP03-3.3BTG.html This latter one seems to be based on TVS diodes alone without BJTs or SCRs. Capacitance is still very low. Sean On Wed, Oct 26, 2011 at 2:18 PM, Bob Blick wrote: > On Tuesday, October 25, 2011 1:55 PM, "Dwayne Reid" wrote: > >> If this is something that you are modifying rather than building from >> scratch, varistors designed for telcom use are useful. =A0The ones that >> I have are about the size of a fat 1/2 resistor and made of green >> epoxy or similar material. =A0The markings on them are "V120-2" and >> they clip at about 1Vp-p. =A0These are nice because the onset of >> clipping is soft and rounded - they are significantly less audible >> than 4- 1n4148 diodes in series / anti-parallel at the onset of >> clipping. =A0Obviously, these varistors are bi-directional. >> >> I purchased probably about 1000 of these green varistors about 30 >> years ago and often wish that I had purchased the whole (large) >> cardboard box - I'm pretty sure that the ones that I didn't take >> eventually made their way to the landfill. >> >> Anyway, I'm pretty sure that the 1Vp-p is a fairly standard telcom >> varistor spec and should work nicely at the nominal -10dBu or -10dBv >> level that your consumer-grade audio equipment is running at. > > I'll look around, but it's hard to find low-voltage ones with low > capacitance. The closest I've come so far is the Littelfuse > V5.5MLA0402LN rated at 5.5 volts which clamps about 10 V (at 1 mA) up to > 39V at 1 Amp and has 70 pF of capacitance. It is specifically intended > for sensors and audio. Most in the same category have ten times as much > capacitance. > > But it should be OK for my needs, which are add-ons to existing gear. > Thanks! > > Friendly regards, > > Bob > > -- > http://www.fastmail.fm - IMAP accessible web-mail > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .