On Sat, 26 Jan 2013 11:24:11 -0700, Jim Thompson
wrote:
On Sat, 26 Jan 2013 13:11:11 -0500, bitrex
wrote:
On 1/26/2013 12:18 PM, Jim Thompson wrote:
What are these nodes?
http://tinyurl.com/bjxndpg
...Jim Thompson
I lurk here mostly, but I don't understand the big deal over this
circuit. Isn't it just a poor man's TIA? Input current against R5
creates current in the output -Iin*R5/R4 so (neglecting the small
current contribution from Iin) Vo/Iin = -(R5*(R3+R4))/R4?
Yes, exactly! A breath of fresh air from someone who knows what they
are doing, instead of BS'ing!
The big deal is that the "bootstrap" is not broadband. It is actually
a "poor man's gyrator", as I've demonstrated. I'm guessing that the
component values were chosen specifically to enhance behavior at
40KHz... that is, the sensor is likely a motion detector type.
So, as a plain vanilla amplifier, it's performance is terrible...
unless driven from a high impedance source... then it's pretty much
useless.
...Jim Thompson
Which is what Bitrex said, and I missed emphasizing, input "current".
As a voltage amplifier it's a differentiator.
...Jim Thompson
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