Electronics > Beginners

Opamp feeding opamp on different PCB's - best way to do this? (Schematic shown)

(1/1)

K3mHtH:
Hey everyone,
I'm working on a schematic where I have an audio signal coming out of an opamp on one PCB that needs to go into an opamp on another PCB. I'm just wondering where is best to make the "break" connection between these two circuits to do it properly.

The audio coming out of the first opamp is 5Vpp. Please see schematic..

rstofer:
I like the first scheme because I would want the signal coming off a board to be as high as possible in terms of voltage and as low  as possible in terms of impedance.

alanambrose:
Yeah, agree - maybe an SMA patch lead?

Mr Evil:
To provide a contrary opinion, Break 2 will be more resilient in the case of a fault. R4 will pull the input of U2A to ground if the connector comes loose, and R3 will limit the current from U1A if the connector is shorted (though TL074 has output short circuit protection, so it would probably survive regardless).

David Hess:
I agree with rstofer; the high signal level with attenuation at the input means that common mode noise (ground noise) is attenuated as well.  Note that you may need a low value series resistor at the source to allow the operational amplifier to drive the line without a local oscillation.

But if ground noise is a problem, then there are two simple and cheap ways to solve it:

1. Use two wires with one being the signal ground, actually common, from the source and then use an instrumentation amplifier at the receiver.  Usually a simple 4 resistor difference amplifier provides sufficient noise rejection.

2. Send the signal as a current instead.  Make the transmitter operational amplifier into a current source, sink, or pump, and provide a resistive load to ground (common) at the destination followed by a buffer.

I have used both methods very successfully when transferring audio signals even between separate chassis.

Navigation

[0] Message Index

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod