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TL082: hi , Its about using tl082 on differential amplifier with single Vcc

Iverson tseng
Prodigy 10 points
Part Number: TL082
Other Parts Discussed in Thread: TLV9101, LM7322, TLV2197-Q1, OPA2197, OPA2192

Tool/software:

Dear sir

Its about using tl082 on differential amplifier with single Vcc(15V and 0v)  ,when input is closed to 0V the output is not stable ,  even up to 4v 

can u tell us why does this happen and how to design the circuits.

  • +1
    Guru 317000 points

    See the input voltage range specification in the datasheet.

    You probably want an opamp with rail-to-rail I/Os like the TLV9101/2.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    but the SR is too slow if i choose Lm7322 can be work on it?

  • +1 in reply to Iverson tseng
    TI__Guru* 77331 points

    Hi Iverson, 

    Iverson tseng said:
    the SR is too slow if i choose Lm7322 can be work on it?

    LM7322 or TLV2197-Q1 should work for the difference amplifier application. These are RRIO op amps. 

    For single supply rail,  here is an example for the difference amplifier.  

    LM7322 Difference Amplifier 09182025.TSC

    If you have other questions, please let us know. 

    Best,

    Raymond

  • +1 in reply to Raymond Zhang1
    Prodigy 10 points

    Appreciate for u advice . i noted the Lm7322 Aol is lower than opa2197 and opa2192 did those two type will be better at this circuit or i just used the Lm7322 is suitable the circuit .

    another question is this circuit necessary? Can i just connect to the GND?

     

  • +1 in reply to Iverson tseng
    TI__Guru* 77331 points

    Hi Iverson, 

    Iverson tseng said:
    Lm7322 Aol is lower than opa2197 and opa2192 did those two type will be better at this circuit or i just used the Lm7322 is suitable the circuit .

    It is up to you based on your requirements. Yes, OPAx197 is the same family as OPAx192, and TLV2917-Q1 is a low cost of OPAx197 version. These are newer op amp design. 

    Iverson tseng said:
    another question is this circuit necessary? Can i just connect to the GND?

    If the circuit has to be designed properly, then it is needed. The node is required so that the op amp's input Vcm range will not be violated (you are using single supply rail). If it is dual supply rail configurations, then the node tied to GND is good. 

    In addition, the node required to have both source or sink in current during input change (though the current is very small). If the output has to following the input change instantly, then the reference is required. Otherwise, it you may see some delay, if input differential signal is changing fast. 

    In the op amp's single supply configuration, some circuits are tied it to GND (as you drew), it may be ok for general purpose design or if the GND is stable and does not exhibit ground bounce or high ripple voltage at the node.   

    If you have other questions, please let me know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 10 points

    thx u for u help and have a good day.