Tool/software:
I'm planning on using the PGA2500 in my design but I don't need a diff. output. Not seeing much about the internal circuitry of this device on the data sheet,
I presume it's ok to just take the positive output of the amp directly? any likely issues in this scenario?
TIA
Hi Ian,
The PGA2500 is intended to be used in fully-differential output configuration, where the device will provide the specified performance.
Although, it is possible to use the device in single-ended output configuration, the resulting single-ended signal will now include any common-mode noise, offsets of the DC servo voltage circuit and errors of the common-mode amplifier. Using VCOM to center the single-ended output at the desired bias voltage, you will connect your circuit to one of the PGA outputs. If you use this approach, the PGA will need to see matched equivalent impedance load by the PGA2500 VOUT+ and VOUT- outputs. When using this approach, the single-ended signal will be at 1/2 of the gain of the PGA2500, and will have additional noise, and degraded AC performance.
A better approach will be to follow the PGA2500 output with a difference amplifier. The difference amplifier accepts the (VOUT+) - (VOUT-) differential voltage signal and performs the fully-differential voltage to single-ended conversion. Use a low-noise, low-distortion amplifier audio amplifier to perform the differential to single-ended conversion such as OPA1655. You will need to bias the VREF reference voltage to center the single-ended output signal. Use a low-noise, low impedance source to drive the VREF voltage of the difference amplifier. Also, use high-grade C0G/NPO capacitors through the signal path to obtain low distortion.
Thank you and Best Regards,
Luis
