THS3491RGTEVM: 15V square wave from 3V3

ahbib

Part Number: THS3491RGTEVM
Other Parts Discussed in Thread: THS3491, UCC27517, UCC27537

Hello

In my project, I try to amplify 3V3 square wave signal (T=100ns %50 DutyCycle) from FPGA. My goal is amplify to signal 15V (>15V, <25V will be enough) amplitude level. I want to see 0-15V square wave on opamp output.

I simulate THS3491 with VCC=25V, VEE=-5V, Rg=200ohm, Rf=1kohm and achive it at 20V. I think my output signal is meet headroom input voltage. But I couldnt understand why I cant get similar result on real pcb. am I missing something?

Appreciate for any help.

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 325980 points

Why did you choose the THS3491? To get a square wave, you could use a comparator, or, if you need high drive strength, a gate driver like the UCC27517 (15 V) or UCC27537 (30 V).

0 Hasan Babiker31 over 5 years ago in reply to Clemens Ladisch

TI__Genius 15605 points

Hello Ahbib,

Can you clarify what results you are seeing from your board? Can you share TINA simulations?

Best,

Hasan Babiker

0 ahbib over 5 years ago in reply to Hasan Babiker31

Prodigy 60 points

Hello Hasan,

Tina circuit and simulation in below and I receive this wave around. No problem with that. But now I have heating problem with opamp. There is no output load but it is heating, 30mA around both supply (-5V,+20V). Do you have any suggestion?

0 ahbib over 5 years ago in reply to Clemens Ladisch

Prodigy 60 points

Hello Clemens, Thank for advice. We want different output voltage with same circuit with different variant. so opamp were proper for project. But I will consider your advice. Thanks again.

Ahmet

0 kai klaas69 over 5 years ago in reply to ahbib

Guru 140200 points

Hi Ahbib,

try this circuit:

ahbib_ths3491.TSC

Kai

0 Hasan Babiker31 over 5 years ago in reply to ahbib

TI__Genius 15605 points

Hello Ahbib,

Are you referring to 30mA supply draw in simulation or are you measuring this on your board?

Best,

Hasan Babiker

0 ahbib over 5 years ago in reply to Hasan Babiker31

Prodigy 60 points

Hello Hasan,

I measure it on board.

Sincerely yours

0 ahbib over 5 years ago in reply to kai klaas69

Prodigy 60 points

Hello Kai,

I tried and changed R7 and R4 but still heating.

Thanks

0 kai klaas69 over 5 years ago in reply to ahbib

Guru 140200 points

Hi Ahbib,

have you added R1 and measured behind R1 (not directly at the output)?

Kai

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

Guru 140200 points

Hi Ahbib,

does it work now?

Kai

0 ahbib over 5 years ago in reply to kai klaas69

Prodigy 60 points

Hello Kai,

opamp is working both way but opamp is still heating.

0 Hasan Babiker31 over 5 years ago in reply to ahbib

TI__Genius 15605 points

Hello Ahbib,

Did you add a series resistor to the output? What is the impedance of the scope you are measuring output with, is it a 50-ohm load?

Best,

Hasan Babiker

0 kai klaas69 over 5 years ago in reply to ahbib

Guru 140200 points

Hi Ahbib,

please show your latest schematic. And please post a photo which shows your modifications carried out on the EVM board.

Maybe you have damaged the OPAmp during experimenting? Then check again with a fresh one :-)

Kai

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THS3491RGTEVM: 15V square wave from 3V3