https://www.newport.com/p/70710. Is the input current noise lower than that of the LT1028 below 1 kHz? Regards, -- Jean-Pierre Coulon
Has anybody tried this transimpedance amplifier?
Started by ●November 16, 2023
Reply by ●November 16, 20232023-11-16
On Thu, 16 Nov 2023 16:26:52 +0100, Jean-Pierre Coulon <coulon@cacas.pam.oca.eu> wrote:>https://www.newport.com/p/70710. > >Is the input current noise lower than that of the LT1028 below 1 kHz? > >Regards,You can buy opamps with noise less than 1 fA/rthz. LT1028 is bipolar, 1000x that noise.
Reply by ●November 16, 20232023-11-16
On Thu, 16 Nov 2023, John Larkin wrote:> You can buy opamps with noise less than 1 fA/rthz.The AD549 has a promising current noise. I must experiment because of is undocumented voltage noise at the frequencies I want. -- Jean-Pierre Coulon
Reply by ●November 16, 20232023-11-16
On 2023-11-16 15:45, Jean-Pierre Coulon wrote:> On Thu, 16 Nov 2023, John Larkin wrote: > >> You can buy opamps with noise less than 1 fA/rthz. > > The AD549 has a promising current noise. I must experiment because of is > undocumented voltage noise at the frequencies I want. >If you post a bit more about what you're actually trying to measure, we can probably be more help. A TIA with 4 pA/sqrt(Hz) noise, 100 kHz bandwidth, and 10**9 ohms transimpedance will have an output noise floor of E_N ~ 4e-12*1e9*sqrt(1e5 * pi/2) = 1.6 Vrms. [The pi/2 is the ratio of the noise bandwidth of a 1-pole rolloff (1/4RC) to its 3-dB bandwidth (1/2piRC).] Viewed on an oscilloscope, that'll look like a 6-V wide stripe down the middle of the display, with outliers up to +-5V at least. Not exactly your state-of-the art low noise amplifier! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
