TLV4172: TVL4172 output is wrong

david zhang

Part Number: TLV4172

I have connected the non-inverted pad of TLV4172 to GND by a 1000Ω resistor and configure TLV4172 as a buffer , the TINA simulation shows the output is around 420uV. I have tested two PCBs and one output is around 0V and another output is -7V which is wrong, Please give me a reson for this wrong result. Many thanks in advance.

over 3 years ago

+1 kai klaas69 over 3 years ago

Guru 140200 points

Hi David,

keep in mind that voltmeters can show a high input capacitance which can make the OPAmp oscillate when directly touching the output. Insert a small isolation resistor as shown in figure 14 of datasheet.

By the way, don't let the other OPAmps in the TLV4172 float

Kai

0 Tim Claycomb over 3 years ago

TI__Genius 15410 points

Hi David,

Try probing the output with a scope and see if you see any oscillation like Kai mentioned.

Did you measure the input voltage and both supplies to make sure they were at the voltages you expect them to be at?

If you input a 1Vpp 1kHz sinewave what does the output look like on a scope? Please provide waveforms of the input and output signals.

Thank you,

Tim Claycomb

0 david zhang over 3 years ago in reply to kai klaas69

Prodigy 50 points

many thanks, I will follw your suggesion. I have let other opamps in TVL4172 float, how shold I deal with it?

0 david zhang over 3 years ago in reply to Tim Claycomb

Prodigy 50 points

many thanks, I will follw your suggesion.

0 kai klaas69 over 3 years ago in reply to david zhang

Guru 140200 points

Hi David,

connect the +inputs of unused OPAmps to signal ground and connect their -inputs to their outputs. As if you would want to connect them as individual voltage followers. At the end you have four voltage followers but only one of them is in operation.

Kai

+1 Tim Claycomb over 3 years ago in reply to david zhang

TI__Genius 15410 points

Hi David,

I recommend taking a look at "The Unused Op Amp - what to do" for more information.

Thank you,

Tim Claycomb

Amplifiers

Amplifiers forum

TLV4172: TVL4172 output is wrong