LIGO Document D060205-v1

Low Noise Preamplifier (fixed errors in schematic)

Document #:
LIGO-D060205-v1
Document type:
D - Drawings
Other Versions:
LIGO-D060205-x0
10 Mar 2008, 00:00
Abstract:
0.7nv/sqrt(Hz) preamp with 10^-14 amp/sqrt(Hz) current noise,
gain=100 bandwidth DC to 20kHz
Files in Document:
Topics:
Notes and Changes:
FET drain and source interchange:

Weiss: THE SOURCE AND DRAIN OF THE IF3602 FET ARE INVERTED. THE DRAIN SHOULD BE WHERE THE SOURCE IS ON BOTH PARTS OF THE FET. ALSO ALL RESISTORS IN THE SIGNAL CHAIN NEED TO BE THIN FILM OR WIREWOUND : R2,R3,R6,R7,R10,R4. THE INPUT 100K IS JUST TO DRAW CURRENT FROM THE GATE, THE REAL IMPEDENCE OF THE SIGNAL SOURCE NEEDS TO BE LESS THAN 10 OHMS IF ONE HOPES TO GET 0.7NV/SQRT(HZ) EQUIVALENT INPUT NOISE.

I MEASURED 0.7NV/SQRT(HZ) FROM 10 HZ TO 10 KHZ EQUIVALENT INPUT NOISE IN THE HAND BUILT PREAMP THAT IS MODEL FOR THIS "MORE"PROFESSIONAL LIGO ENGINEERED VERSION.

ONE CAN USE A TRANSFORMER IF YOU NEED TO GET TO LESS THAN 0.7NV/SQRT(HZ). IT NEEDS TO BE A GEOFORMER WITH GOOD MUMETAL SHIELDING AND LOW REAL IMPEDENCE WINDINGS. UTC TRANSFORMERS ARE NOW SOLD BY HAMMON


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