LM7171: 20v amplification :Op-Amp negative Voltage

ashish gopal

Part Number: LM7171

I am using IC LM7171A to generate 20v output pulse from 3.3v input (uni-polar). Below is the schematic . Do I need to connect -24v (NEG) to pin 4 of op-amp to make this work?

Thank you

Ashish.G

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Ashish,

according to the datasheet the input voltage must stay 1.65V away from the supply rails. And the output of LM7171 cannot reach the supply rails either. Please take a look into the datasheet of LM7171. So, yes, you will need some negative supply voltage. With a 1k load you should have a negative supply voltage of at least -2.5V, better -3V. With a 100R load you will need a negative supply voltage of at least -6V.

Kai

0 ashish gopal over 5 years ago in reply to kai klaas69

Prodigy 130 points

Hi kai

Can you suggest any inverter IC which would generate 24v(NEG) vout from positive 24volt input?

0 Michael Steffes over 5 years ago in reply to ashish gopal

Guru 48395 points

You cannot put 48 V across this device, As Kai said, -5V supply would probably give you the necessary I/O headroom.

Also, those resistor values are way too high for stability in this high speed part, you need to get those down a lot, R2033 should be more like 100ohm then calculate the feedback from there.

0 ashish gopal over 5 years ago in reply to Michael Steffes

Prodigy 130 points

Thank you Michael Steffes and Kai

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LM7171: 20v amplification :Op-Amp negative Voltage