Relays will always cause clicks.
just did this on the bench-- you're correct. even if the opamp is ac connected the momentary switching causes a momentary dc shift.
I forgot about the DC offset shift! Changing the DC noise gain will change the DC offset, and make a click without any signal.
You can minimize that if you arrange for the DC gain to be low (AC couple the gain network), but there will still be a slight offset shift, just a very small one.
You can minimize that if you arrange for the DC gain to be low (AC couple the gain network), but there will still be a slight offset shift, just a very small one.
Mouser says obsolete, Fairchild has 0 stock.Have you looked at Fairchild H11F1N FET optocoupler with symmetrical output curves?
Is there a new number?
Panasonic makes PhotoMOS relays, and IIRC, some of them use symmetric FETs for AC signal switching. Using symmetric FETs and their inherently floating optical 'gate' control, they can be extremely linear. Here's a simple link: PhotoMOS Relays - Panasonic | Mouser
These will work, but they're priced around the same as a mechanical relay. However, they will behave much more predictably, will never wear out, or be subject to interference due to an adjacent device (relay coils of neighboring devices can alter each other's turn on and turn off times depending on the coil state.)
If you only need a few switches, PhotoMOS can work well, in some ways better than relays. Not sure if they can be made to do a slow turn on or turn off, but they are definitely more predictable than any relay.
These will work, but they're priced around the same as a mechanical relay. However, they will behave much more predictably, will never wear out, or be subject to interference due to an adjacent device (relay coils of neighboring devices can alter each other's turn on and turn off times depending on the coil state.)
If you only need a few switches, PhotoMOS can work well, in some ways better than relays. Not sure if they can be made to do a slow turn on or turn off, but they are definitely more predictable than any relay.
Regarding the H11Fxx optocoupler, Fairchild opto line was absorbed by On Semi, and the part numbers changed somewhat.
On Semi now carries the devices as H11F1M with PN variations for SMT and wide pinout. Go to Mouser, pull the latest data sheet and select what you need. One piece price just under $3.00US.
On Semi now carries the devices as H11F1M with PN variations for SMT and wide pinout. Go to Mouser, pull the latest data sheet and select what you need. One piece price just under $3.00US.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Source & Line
- Analog Line Level
- Switchable opamp gain