Morning Mr. Zhang,
That equation came out of some work I was doing back inthe 1996 time frame - published in a series of articles, but summarized in this design presention - those articles are referenced in the end of this, the theme of this treatment…
In theory yes, in practice though the 2nd stage adds very small input referred noise. Once upon a time I tried to detail all of that here,
https://www.edn.com/controlling-spot-and-integrated-noise-in-a-two-stage-transimpedance-design/
The THS4601…
I sort of glanced at those Tim, they are kind of bouncing around looking at stability mainly I think, If you set out to deliver a butterworth closed loop response, the transimpedance design flow is pretty simple, take the circled equation here and solve…
As Kai said Hari, you need to complete the design with a source C and feedback Cf. In general, you end up with a 2nd order transfer function modeling the op amp as a single dominant pole - this is a good simplification for most designs as the feedback…
That is going back a ways - Tony actually died of lung cancer back in 1995
Here is what you need, 6175.Transimpedance design flow using high speed op amps.pptx
No way to say without a source capacitance. And 10u seems crazy high for any transimpedance design. What signal bandwidth do you need. If your current source has no capacitance (odd) then we would just use the op amp parasitic C for design - jumping way…
I think that development is missing a Root(2) term - this was the classic development to put the feedback pole at the intersection of the noise gain and Aol curve - that will yield a Q = 1 design, I have tried to purge this error for over 24 years, with…
Well Kenneth
The equivalent input current noise for a transimpedance design is a lot more than just the current noise term - often the output noise is dominated by the input voltage noise getting a peaking gain to the output.
Transimpedance design…
You are of course kidding me Paul,
Your example circuits are transimpedance designs where the source C is a big part of the response equations.
And actually, if I had to guess I would bet they are under 10pF and what I would probably due (lacking…
Well Selvedin,
The numerator is just the ideal gain from a current input to the output via Rf||Cf = Zf
The denominator is the 1+(1/LG) term where the key part is the diode source C getting into the noise gain,
This file is a later summary of all…
