I have a non-inverting amplifier circuit shown in picture. This circuit has an input wave (-/+ 5V) and output needs to be 0 to 3.3V. I'll be using zener diode (LM 385) as my voltage reference. But I don't really know how zener diodes work. And I will need to decide the resistor values as well. If anyone could help, I would really appreciate it, whether a link, or suggestion to the circuit itself, I appreciate it.


  • \$\begingroup\$ Which version of the LM385 are you using? There's an version adjustable between 1.25V and 5.3V, and fixed voltage versions such as 1.25 and 2.5V. There may well be others. \$\endgroup\$ Dec 11, 2023 at 16:19
  • \$\begingroup\$ This circuit won't work for inputs less than +2.5V, because the reference diode must always be reversed biased. \$\endgroup\$ Dec 11, 2023 at 16:20
  • \$\begingroup\$ Maybe first try using a voltage source instead of D1. Once you get your expected output from the rest of the circuit, then work on making a offset reference that works with your circuit. \$\endgroup\$
    – Aaron
    Dec 11, 2023 at 17:30
  • \$\begingroup\$ I am using LM385-2.5V. My input is 5V so I think I'm good with that. I already got my desired output using just a voltage source(6.67V), but this diode(2.5V) is what I have available. \$\endgroup\$
    – luffy
    Dec 12, 2023 at 19:43

1 Answer 1


A simple resistive divider may be good enough here, optionally followed by a buffer amplifier.


simulate this circuit – Schematic created using CircuitLab


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