I saw this LM317/337 Servo Rectified Filtered Power supply board for sale.
LM317 / LM337 +/-1.5V~37V Adjustable Dual Voltage Regulator Power Supply Module 699985741185 | eBay
As usual, the seller does not include any schematic. How does the LF353 servo opamp work in this PSU circuit? What advantage does it have over the simple LM317/337 PSU?
The target application is a headphone amplifier using class A circuit.
LM317 / LM337 +/-1.5V~37V Adjustable Dual Voltage Regulator Power Supply Module 699985741185 | eBay
As usual, the seller does not include any schematic. How does the LF353 servo opamp work in this PSU circuit? What advantage does it have over the simple LM317/337 PSU?
The target application is a headphone amplifier using class A circuit.
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Hello.
I think it use this schematic (IC2 is LM337) .
The opamp is used to maintain the same voltage despite variations.
For example, if LM317 output is +14,3V it adjust LM337 for -14,3V.
I think it use this schematic (IC2 is LM337) .
The opamp is used to maintain the same voltage despite variations.
For example, if LM317 output is +14,3V it adjust LM337 for -14,3V.
As concluded by samsara, the OPAMP is used to make one voltage track the other but with opposite polarity.
Using a double potentiometer would leave close to the same result.
Using a double potentiometer would leave close to the same result.
Keilau, I think the purpose of the opamp in the schematic you show for "servo, rectifier, filter power supply board" is to take the ripple and noise from the output of the power supply, invert it, and feed it back into the lm317/337, thereby cancelling the ripple and noise on the output. Hence the "servo" in the title. I think the circuit was originally designed by a poster on this forum, maybe apex audio, but I'm not sure.
chalky, I agree with you that the servo in the PCB seller posted circuit is likely for noise and ripple reduction. In this circuit, the servo takes the input from the same side of the output rail. I hope that some user may take some measurement of the LM317/337 pair with and without the servo to see how effective it is.
The servo can be used for output rail balance tracking as samsara suggested using his schematic. But it is a different topology. In the samsara schematic, there is only one trimmer on the positive side for output rail voltage adjustment.
When I tried to build a +/-15V PSU many years ago using the LM78xx/79xx pair, I could not get a close enough match of the output rails. I ended up using a very expensive tracking voltage regulator, Raytheon RC4195TK.
You right, it's the right schematic, not mine.
Here it show complete PCB
LM317/LM337 DC Servo Adjustable Voltage Regulator Board, Positive and Negative Dual Band Rectification Filter-in Air Conditioner Parts from Home Appliances on Aliexpress.com | Alibaba Group
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