I'm trying to reproduce an "ultra" low-noise amplifier circuit which calls for several precision amplifiers/modulators (AD549/LF356/AD630). The input source is a Hamamatsu S1223 photodiode capturing a faint optical signal which is oscillating at 1kHz. While the datasheets for these components have many useful suggestions, I do not see a clear recommendation as to what passive components should be used.

After reading this design reference, I'm thinking to settle on all NP0 capacitors and metal film resistors. However, I'd really appreciate if anyone with experience can comment on what the best choices are? (i.e. If some exotic "tantalum" or "mica" capacitor would make a big difference in noise, I'd love to know!)

The circuit is given below. The signal is amplified (AD549), then bandpass filtered (LF356), then frequency-locked (AD630), and finally low-pass filtered (LF356).

Thanks so much!

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  • \$\begingroup\$ Look up capacitor microphonics and choose your capacitors in the signal path with care. Not specifying the signal input level means this problem is under-defined. \$\endgroup\$ – Andy aka Aug 20 '19 at 7:01
  • \$\begingroup\$ You are planning to use electric-field shielding, right? and probably sheet steel, for magnetic field shields? \$\endgroup\$ – analogsystemsrf Aug 21 '19 at 6:19
  • \$\begingroup\$ what is your budget for repetitive noise, such as power supply hum, or switching regulator trash at 100,000Hz or even the ringing at 10MHz? \$\endgroup\$ – analogsystemsrf Aug 21 '19 at 6:25

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