Hi

I am trying to make a sensitive phase detector I am inputting 2 x 5 Khz signals into a SA612 this device does have a differential output but I am only using one output this is then 10 Khz after the mixer I am then low passing to about 5 herts and the other circuit you already have my problem is there is only about 1mv per 1 degree(of shift) I an trying to get this up so I can see .1 degree of movement or more.

Thanks for your help

You should probably make use of the differential output. You can try powering the device from the same regulator I posted earlier, but you may suffer from things like drift that will still give you heartburn.
Can you post a link to the sensor?

 

What are you

Hi

I am trying to make a sensitive phase detector I am inputting 2 x 5 Khz signals into a SA612 this device does have a differential output but I am only using one output this is then 10 Khz after the mixer I am then low passing to about 5 herts and the other circuit you already have my problem is there is only about 1mv per 1 degree(of shift) I an trying to get this up so I can see .1 degree of movement or more.

Thanks for your help

1) What is the 5V coming from? How are you regulating your power supply?

2) You really, really, really (really!) need to either increase the value of C3 in your schematic (a lot) or derive your + terminal bias from a zener or micro-regulator as @ronv has suggested. Until you do something about that reference voltage, the other stuff is IMHO kind of futile.

 

What are you


1) What is the 5V coming from? How are you regulating your power supply?

2) You really, really, really (really!) need to either increase the value of C3 in your schematic (a lot) or derive your + terminal bias from a zener or micro-regulator as @ronv has suggested. Until you do something about that reference voltage, the other stuff is IMHO kind of futile.

@DPJ
Prove how noisy your MCP6041 is. Remove C2. Disconnect R1 from your mixer circuitry. Connect a 1K resistor from the R1 input point to +5V; connect another 1K from the R1 input to ground (e.g. at C1). Adjust RV1 for an output of 2.5V at U1:6. Observe signal at pin 6. At pin 6 what is the level of the low frequency noise of which you complained? Under these conditions, each input of the op-amp is presented with roughly the same "noise" from the +5V source (i.e. about 1/2). If the noise source is the +5V, what you now see should be less than usual of the low frequency noise as some/much of it should be rejected by the differential input of U1. If the noise source is the MCP6041, then you should still see the same amount of low frequency noise that you have complained of.