Diode protection: Quick Question

2sb18 · 2nd March 2006, 07:20 PM

Hi,

I want to use two diodes to protect the inputs of an opamp. If I don't put a resistor in the feedback loop, does this render the protection diodes useless?

Thanks,

Steve.

JensRasmussen · 2nd March 2006, 07:25 PM

Steve,

I would use two diodes.

One from the positive rail to input (Cathode on rail) and one from negative rail to input (Anode on rail)

This way you can not exceed the inputvoltage above the railvoltage.

\Jens

Nordic · 2nd March 2006, 07:27 PM

Would this in any way affect the sound, and is this a principle you would use yourself Jens?

JensRasmussen · 2nd March 2006, 07:31 PM

Sound should be ok if the signal is well below the rail voltage (as they should be on an input terminal)

I have used this before to protect opamps for overvoltage on inputs.

\Jens

2sb18 · 2nd March 2006, 07:44 PM

Thanks Jens,

I've attached a more complete schematic. It's single supply. I have a low pass filter before the opamp. For the diodes, I was thinking of using 1N914s. Is that a good choice?

Steve.

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2nd March 2006, 07:25 PM	#2
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Steve, I would use two diodes. One from the positive rail to input (Cathode on rail) and one from negative rail to input (Anode on rail) This way you can not exceed the inputvoltage above the railvoltage. \Jens

2nd March 2006, 07:27 PM	#3
Nordic diyAudio Member Join Date: Sep 2005	Would this in any way affect the sound, and is this a principle you would use yourself Jens?

2nd March 2006, 07:31 PM	#4
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Sound should be ok if the signal is well below the rail voltage (as they should be on an input terminal) I have used this before to protect opamps for overvoltage on inputs. \Jens

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