LM723 ripple performance

[Adam Stouffer]

Looking over the LM723 datasheet shows that it has better ripple
rejection than standard 3 leg regulators.

http://cache.national.com/ds/LM/LM723.pdf

This is done with a 5uf bypass cap across the non inverting input and
ground as seen in fig 1. The caption says its good for 2-7 volts. To go
above 7v the setup is different as seen in fig 2. Can the cap be used in
the same place and also achieve the same performance?


Adam

 

[Phil Allison]

"Adam Stouffer"

Looking over the LM723 datasheet shows that it has better ripple rejection
than standard 3 leg regulators.

** The LM317 has a typical PSRR of 80 dB with a 10uFcap on the adj
terminal.

http://cache.national.com/ds/LM/LM723.pdf

This is done with a 5uf bypass cap across the non inverting input and
ground as seen in fig 1. The caption says its good for 2-7 volts. To go
above 7v the setup is different as seen in fig 2. Can the cap be used in
the same place and also achieve the same performance?

** Using an RC LPF on Vref will definitely reduce hum and noise.

The final result depends on the circuit set up and actual output voltage.

BTW

Both my home brew variable bench PSUs ( 2 to 20 volt @ 2amps) ) use LM723s
and a pass transistor - with variable current limiting from 100mA up.




.......... Phil