Can you measure a LM3886 to see if its ok?

CJ900RR · 6th April 2008, 09:12 PM

I have a bunch of LM3886, some is ok some is not. Can I measure them someway to see if they are ok?

sek · 6th April 2008, 11:27 PM

Hi Calle,

you could make a test jig to quickly mount the chips and power it from a lab supply. All the circuit then needs is a closed feedback loop and a mute resistor. Keep in mind that the LM3886 is only stable at gains greater than 10, better 20. You could mount the whole circuit P2P to a socket, only four resistors and a dummy...

Regarding the LM3886's behaviour, it should "unprotect" (i.e. draw it's nominal idle current) as soon as either supply voltages exceed +-9V. It should unmute at around -10mA current out of pin 8 (to the negative supply).

From there on, it should simply amplify.

You could then, on top of that, test the protection circuits like undervoltage lockout (with the supply lines below +9V or above -9V, respectively) or SPiKe (slowly raise the input signal while driving a low impedance test load, clipping should look like in the datasheet, watch your supply voltage level and heatsinking).

Cheers,
Sebastian.

6th April 2008, 09:12 PM	#1
CJ900RR diyAudio Member Join Date: Jan 2006	Can you measure a LM3886 to see if its ok? I have a bunch of LM3886, some is ok some is not. Can I measure them someway to see if they are ok?

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6th April 2008, 11:27 PM	#2
sek diyAudio Member Join Date: May 2003 Location: Berlin	Hi Calle, you could make a test jig to quickly mount the chips and power it from a lab supply. All the circuit then needs is a closed feedback loop and a mute resistor. Keep in mind that the LM3886 is only stable at gains greater than 10, better 20. You could mount the whole circuit P2P to a socket, only four resistors and a dummy... Regarding the LM3886's behaviour, it should "unprotect" (i.e. draw it's nominal idle current) as soon as either supply voltages exceed +-9V. It should unmute at around -10mA current out of pin 8 (to the negative supply). From there on, it should simply amplify. You could then, on top of that, test the protection circuits like undervoltage lockout (with the supply lines below +9V or above -9V, respectively) or SPiKe (slowly raise the input signal while driving a low impedance test load, clipping should look like in the datasheet, watch your supply voltage level and heatsinking). Cheers, Sebastian.