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Replacement of a discrete component OPAMP with a suitable OPAMP

MANISH KUMAR43
Prodigy 20 points


Background of usage:

We have a cycle converter made in 1980's and its control system has op-amps made up of discrete components. I want to find a suitable replacement of these op-amp cards. The complete data is not available for the op-amp, but I think we have the sufficient 

Details of OPAMP:

  1. Power I/P: +50 V, 24 MA, + load current

                               -50 V, 30 MA + load current

  1. Signal I/P: +/- 0.66 MV; +/- 6.6 810^-3 Amps for full output range (DC)
  2. Output: +/- 30 V, +/- 10 MA
  3. Frequency Response:
  4. 10 K input at feed back   285 KC typical
  5. 100 K input at feed back   65 KC typical
  6. 1 MEG input at feed back   7.6 KC typical
  7. Gain bandwidth (open-loop) greater than 800 KV
  8.                                                                        

 

 

Temp drift:

Input Current           

Input Voltage
  1. 0 to 25

 

-1.5 +/- 2 * 10^-9 amps /

+/- 20 * 10^-6 volts /
  1. 25  to 70

 

+/- 2 * 10^-9 amps /

+/- 20 * 10^-6 volts /
  1. 24 hr drift ( 25

 

+/- 25 * 10^-9 amps

+/- 250 * 10^-6 volts

 

6.  Recovery from 100 V input                         Recovers to 1 % of final value in

  1. 10 K input at feed back                    0.06 millisec (typical)
  2. 100 K input at feed back                 0.10 millisec (typical)
  3. 1 MEG input at feed back                0.40 millisec (typical)

 

7.  Recovery from shorted output                   Recovers to 1 % of final value in

  1. 10 K input at feed back                    0.2 millisec (typical)
  2. 100 K input at feed back                 0.15 millisec (typical)
  3. 1 MEG input at feed back                0.5 millisec (typical)

 

  1. Output impedance:                                      Typical less than 100 ohms

      (open loop)                                                   from DC to beyond 1 Megacycle

 

9. max capacitive load: 200 pfd

 

10. Freq limit at max amplitude:

  1. Resistive load (3.3 K)                     70 KC (typical) (12 v/microsec. Slew rate)
  2. 680 pfd load                                     35 KC (typical) (6 v/microsec. Slew rate)
  3. 100 ohm, 0.01 MFD series load    3.5 KC (typical)

 

 

 

11. Noise at O/P                                                3 mv due to amplifier alone

      ( 100 K input at feedback)

 

12. Common mode input : +/- 8 volts maximum

 

13. Common mode rejection: can be adjusted for more than 120 dB at DC.

 

These are taken directly from the old data sheet available, other curves are also available if required.

can someone help me select a suitable replacement opamp. i have other dual opamp cards as well for which we can discuss later.

Regards

Manish Kumar

 

  • 0
    TI__Genius 12631 points
    Hello Manish,

    Your output seems to suggest a +/-30V output. That requires a minimum 60V supply. We don't have anything remotely close to that in the high speed team. I may be reading this wrong...can you please send the actual datasheet with curves so I can better understand.

    -It looks like the power supplies are +/-50V...is that correct?

    -Frequency response...is KC the same as KHz?

    -I am not sure what gain bandwidth of 800KV means....usually Gain bandwidth is specified in KHz/MHz.

    -Samir
  • 0 in reply to Samir Cherian
    Prodigy 20 points

    Thanks a lot for your reply. here is my reply, but i doubt this will help as i too have a very limited information.


     Your output seems to suggest a +/-30V output. That requires a minimum 60V supply. We don't have anything remotely close to that in the high speed team. I may be reading this wrong...can you please send the actual datasheet with curves so I can better understand.

    I have typed the complete data sheet what i have. it is a GE OPAMP CARD made in 1980's so that is what is available, i understand it is very limited. use of kc might have been common at that time i guess which might be equivalent of kHz(just a guess).

    -It looks like the power supplies are +/-50V...is that correct? YES

    -Frequency response...is KC the same as KHz?  I guess it means the same. it was mentioned in the data sheet as KC so i wrote it as KC.

    -I am not sure what gain bandwidth of 800KV means....usually Gain bandwidth is specified in KHz/MHz. it was a typo for KC

    can i have your email id so that i can send the scanned copy of the curves.

    regards

    manish kumar

    mkumar@pppl.gov

  • 0 in reply to MANISH KUMAR43
    Genius 3295 points
    Hi,

    "KC" stand for "kilocycles" and yes, it was used before "Hertz".

    I hate to do this because I am a "TI" guy... If you really want a monolithic substitute, take a look at the LT6090 and the LT2057HV.

    If you want a discrete replacement that's "up to date" in design and handles high voltage we can design that for you. PM me for more info.

    Mike T.