I have two boards (microphone amplifier and speaker driver) that require +/-15 VDC. The max current required for the boards is 500 mA. Since low-noise dual power supply devices are hard to come by, I'd like to modify my system to accept a single power supply. Ideally, what I'd like to do is design the following chain:
- Input from the AC mains would be via a high-end SMPS (with switching frequency in the MHz range) with an output of 36 VDC.
- A virtual ground would be provided using a TLE2426. A current boosting BUF634 feedback loop to get up to 250 mA as described in https://tangentsoft.net/elec/vgrounds.html would be used. Note that this can be stacked with a second BUF634 to get up to 500 mA. This would provide +/-18VDC rails.
- I would then use LT3090 and LT3045 LDO regulators to further drop the voltages to +/-15VDC rails that feed into the board. The LDO regulators are very high PSRR devices with ultra low noise outputs.
Questions:
To minimize cross-talk between the microphone amplifier and speaker drivers, each device should have their own power rail splitter and LDO regulators (this is also necessary because of the max current capabilities of of the regulators and buffers). Can they share a common SMPS, or should each have their own?
Should this setup work well for powering devices that work in the frequency range 100 Hz to 100 kHz (this is for auditory research experiments at a university, so we have to deal with frequencies above the audible range of humans as well)?
An alternate approach would be to use the TPS7A47 ultra low noise LDO (which can accept up to 36 VDC input). In this case, I could then use the following chain: SMPS -> TPS7A47 -> TLE2426 + BUF634 -> board. However, would this be OK or would there be higher noise in the circuit due to placing the TLE2426 + BUF634 after the LDO?