Chopper Op Amps—are they really noisy?

Ori-san— Agreed, the diagram of the 25-year-old TLC2654 shows what we would now call an auto-zero-type topology. This technique periodically shorts the input of a correction amplifier, storing its output offset on capacitors (external capacitors, in this case), then subtracts the offset from the active signal path in the next cycle of the clock. The term “chopper” has been used somewhat casually through the years to describe a variety of clocked zeroing techniques. It’s not entirely clear whether the author of this old data sheet made a mistake, or perhaps the terminology has gained greater clarity over the years.  — Bruce

Ori-san— Agreed, the diagram of the 25-year-old TLC2654 shows what we would now call an auto-zero-type topology. This technique periodically shorts the input of a correction amplifier, storing its output offset on capacitors (external capacitors, in this case), then subtracts the offset from the active signal path in the next cycle of the clock. The term “chopper” has been used somewhat casually through the years to describe a variety of clocked zeroing techniques. It’s not entirely clear whether the author of this old data sheet made a mistake, or perhaps the terminology has gained greater clarity over the years.  — Bruce