I am in the process of designing a linear power supply.
I am using circuit board relays to switch in 3 different feedback voltage dividers for fixed 5V, fixed 12V and Vadj which will be an external potentiometer.
I have not designed the current limiting or short circuit protection circuitry yet, but i will.
Here are my issues.
1. Lets say i set fixed 12V for 12.05V. It will hold the voltage at that point as long as the circuit is energized. If i turn the circuit off for 5 minutes and turn it back on the output seems to have climbed a few hundred mV and then drops down slowly back towards the set voltage. This problem only seems to happen with the 741 opamp, i was using a 358 before and it would not do it. The 741 provides my circuit better load regulation than the 358, that is why i am experimenting with the 741 as my pass transistor driver.
2. When i connect a 7 ohm test load to my power supply with 12.05V the output drops by 10mV which is not a big deal. However when i disconnect the load the output voltage will eventually start to drop slowly. Somewhere around 10mV per minute
any insight or suggestion would be awesome!
Thanks
I am using circuit board relays to switch in 3 different feedback voltage dividers for fixed 5V, fixed 12V and Vadj which will be an external potentiometer.
I have not designed the current limiting or short circuit protection circuitry yet, but i will.
Here are my issues.
1. Lets say i set fixed 12V for 12.05V. It will hold the voltage at that point as long as the circuit is energized. If i turn the circuit off for 5 minutes and turn it back on the output seems to have climbed a few hundred mV and then drops down slowly back towards the set voltage. This problem only seems to happen with the 741 opamp, i was using a 358 before and it would not do it. The 741 provides my circuit better load regulation than the 358, that is why i am experimenting with the 741 as my pass transistor driver.
2. When i connect a 7 ohm test load to my power supply with 12.05V the output drops by 10mV which is not a big deal. However when i disconnect the load the output voltage will eventually start to drop slowly. Somewhere around 10mV per minute
any insight or suggestion would be awesome!
Thanks
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