THS4140: differential input

Arie Menscher

Part Number: THS4140
Other Parts Discussed in Thread: THS4130

During debug on our board, of output value different than expected at the amplifier output, we have disconnected the differential input of the amplifying circuit from the original source,

and tied to GND, as shown in diagram:

We measure on our board, at amplifier input, 4mV instead of '0'V as expected (difference between positive and negative).

What could be the cause for this?

Thanks,

over 6 years ago

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Arie,

if you measure directly at the input pins of THS4140, then this is the input offset voltage. See the "Electrical Characteristics" on page 3 of datasheet. This is absolutely normal.

Kai

0 Arie Menscher over 6 years ago in reply to kai klaas69

Prodigy 200 points

Thanks for reply, yes it is within the datasheet specification.

0 Arie Menscher over 6 years ago in reply to Arie Menscher

Prodigy 200 points

Hi,

We have simulated the circuit (using the device model with TINA) before posting the question, but were unable to see the input offset voltage as specified by data sheet, got '0' V- should we be able to do so?

Thanks,

0 kai klaas69 over 6 years ago in reply to Arie Menscher

Guru 140200 points

Hi Arie,

you will see an offset voltage when you measure between one input and signal ground.

Not all models simulate all typical parameters like offset voltage, input bias current, input offset current, and so on...

Kai

0 Arie Menscher over 6 years ago in reply to kai klaas69

Prodigy 200 points

Thanks for your feedback.

Arie

0 Arie Menscher over 6 years ago in reply to Arie Menscher

Prodigy 200 points

Hi,

Is there similar device to THS4140 available, pin-to-pin compatible and same supply, with lower

input offset voltage (specifically, lower than 500uV instead 1 to 7mV) all other parameters remaining same?

Thanks,

Arie

0 kai klaas69 over 6 years ago in reply to Arie Menscher

Guru 140200 points

Hi Arie,

what do you need such a 160MHz differential I/O amplifier for? Would a simple OPAmp also do the job? Is the wide bandwidth needed?

Kai

0 Arie Menscher over 6 years ago in reply to kai klaas69

Prodigy 200 points

Hi,

While the initial design is not mine, the bandwidth has been specified to enable also future support, but to address the second question (simple OpAmp), I would like to find an alternative without a re-design involved, therefore my question about pin-2-pin compatible, same supply ,etc.
Is there such option, with lower bandwidth ?

Thanks,
Arie

0 Hasan Babiker31 over 6 years ago in reply to Arie Menscher

TI__Genius 15565 points

Hello Arie,

The THS4130 would be your best bet if offset voltage is your primary concern. Both amplifiers have the same pin configuration,and the THS4130 has an offset voltage of 2mV. Here is a comparison:

5127.Compare Parts.pdf

Best,

Hasan Babiker

0 Arie Menscher over 6 years ago in reply to Hasan Babiker31

Prodigy 200 points

Thanks a lot, I will check it.

Arie

Amplifiers

Amplifiers forum

THS4140: differential input