Nope, you use two cascaded RC lowpasses in the base lead. It has a total of three lags in the loop...you have to make the op amp really slow to avoid oscillation. You win by a factor of C_CE/C_bypass, which can easily be 10**7.
Cheers
Phil Hobbs
Understood--at all signal frequencies you're stuck with the behaviour of a barefoot BJT follower. OTOH that isn't so bad for a lot of things, especially frond end amps for photodiodes and other sensors with a lot of capacitance to worry about. It sure helps the PSR of op amps!
Cheers
Phil Hobbs
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hI see. My version of the circuit requires that the reference be quiet. Yours doesn't.
Yup--voltage references are horribly noisy--even worse than 300 kelvin resistors. You can get nanovolt noise at frequencies where you care about it, for things like photodiode biasing and discrete circuitry with poor supply rejection.
Cheers
Phil Hobbs
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Band gaps are really bad. 1.xxV with 500nV/sqrt(Hz) is a lot worse than 6.xxV with 100nV/sqrt(Hz)
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