Manufacturer of Low Noise JFETs

[analog_guy]

Is anyone familiar with Moxtek? They advertise really low noise jfets (En <0.5 nV/sqrt(Hz) in either TO72 packages or loose dies. They have a website describing their devices, and their intended application is very different from audio: the front end amps for SiLi and GeLi x-ray spectrometers. They make only n-channel devices, and I bet they are not cheap.

http://www.moxtek.com/PDF/JFETs/DAT-MX%20JFETS.pdf

[janneman]

Intriguing. I wonder what the 'reset' and 'feedback' pins do?

jd

[Samuel Groner]

En < 0.5 nV/sqrt(Hz)

I don't see any part meeting this spec; MX-16 is 0.6 nV/sqrt(Hz) typ. at 10 kHz and -100° C. It seems they have low capacitance though (which is important for charge amplifiers as far as I know).

Samuel

[Samuel Groner]

I wonder what the 'reset' and 'feedback' pins do?

I'd say just brought out additional gate connections for low stray capacitance. Charge amplifiers have capacitive feedback (with very low feedback capacitances possibly below the pF range), and the reset pin is used to inject a pulsed charge to zero the amplifier output in order to prevent it from saturation.

Samuel

[juma]

Cheap and common BF862:
0.8 nV/sqrt(Hz) at 100kHz and 25° C.
http://www.nxp.com/documents/data_sheet/BF862.pdf