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Offset a Digital signal (0 and 5 V ) by approximately 70V DC

NEERAJ KUMAR
Intellectual 355 points
Other Parts Discussed in Thread: OPA453, OPA454

Aim: I have to design a circuit which can offset a digital signal (0 and 5V) by approx 70V DC. In other words, input is of 0 and 5 v and output should be 70V and 75 volt. The frequency of this signal is 10 Mhz .

Approach :

I thought of using opamp and use it as adder. I could design it easily using High Voltage amplifier like OPA454, OPA453 etc.

But the problem is, they have very low slew rate(around 15V/us). I doubt it will be able operate on a frequency around 10Mhz.

I searched for other opamps as well using Opamp selection tool, but if i chose higer slew rate, Vcc value was lower (i.e. can't obtain higher voltage, opamp would saturate on voltage around 70V)

Is there any other opamp available for above case or any other approach?

  • 0
    TI__Guru* 93105 points

    Hi Neeraj,

    Keep in mind that if you are trying to faithfully reproduce a 10 MHz digital waveform with an op amp than its bandwidth and slew rate are going to have to be much higher than what is required to reproduce a 10 MHz sine wave. Even for a 10 MHz sine wave a slew rate of about 150 V/us (5 Vp-p signal) would be required. That is well beyond the 13 V/us slew rate of the OPA454.

    TI doesn't have an op amp that can can cover the very high voltage and speed requirements of your application. When we find that is the case, we sometimes suggest that the person making the inquiry check with Apex Microtechnology. They are not a direct TI competitor and we have no affiliation, but we at TI think it is always best to help try and help our customers with their applications solutions even if it means directing them to another company. Apex offers a wide line of high-voltage, high-speed amplifiers, one of which would likely resolve your application need. See the following web page:

    Regards, Thomas

    PA - Linear Applications Engineering