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TLC2272 performance

Patrick Simmons
Mastermind 26335 points
Other Parts Discussed in Thread: TLC2272, OPA4171

Hello team,

My automotive client is curious as to why the TLC2272 has faster recovery than the OPA4171 when the inputs are returned from being pulled out of the common mode range.  Can anyone shed some light on this?

Thanks in advance,

-Patrick

  • 0
    TI__Guru* 93105 points

    Hi Patrick,

    The TLC2272 and OPA4171, although both CMOS op amps, have very different designs and their input overload recovery behaviors, especially when exceeding the specified common-mode voltage range can be very different. Likely, it wasn't a prime design consideration. So how long it takes to recover is mostly related to how charges get stored in the various junction capacitances during the input/output overload time, and then how quickly they can be removed. The charge and discharge times come down to the currents available during those times, and they are dictated by the specific op amp design and particular CMOS process used to fabricate the integrated circuit.

    As I mentioned, the TLC2272 and OPA4171 use very different designs, and they are fabricated on completely different CMOS processes. Some points about them:

    • The OPA4171 uses complementary P-channel/ N-channel differential input pairs. The TLC2272 uses a conventional P-channel differential input pair. These are very different designs.
    • The OPA4171 has input-to-input differential over-voltage diode clamps, the TLC2272 doesn't.
    • The operating current of the OPA4171 is specified as 475 uA, and for the TLC2272 about 1.2 mA/ amplifier. 

    These, and other circuit/process differences, will result in different input overload recovery times.

    Regard, Thomas

    PA - Linear Applications Engineering