Maker Pro
Maker Pro

LTC1050 to NJM2904D circuit

DalSegno

Jan 14, 2018
2
Joined
Jan 14, 2018
Messages
2
Im trying to build a "Transimpedance amplifier for converting current to voltage" and it uses LTC1050 op-amp in the circuit, but I cant manage to get one and bought a NJM2904D which is also a single supply voltage op-amp. upload_2018-1-14_18-4-16.png
This is the original circuit Im trying to copy. But I dont have LTC and I have NJM so how should I wire it? And probably how to put it into a breadboard and where do I put ground pin because Im using Arduino to record the voltage output.
 

Audioguru

Sep 24, 2016
3,656
Joined
Sep 24, 2016
Messages
3,656
The LTC1050 single opamp has Jfet inputs so it has almost no input bias current, then the photodiode is very sensitive to low light levels. But the NJM2904 dual opamp is the same as an LM358 or LM2904 dual opamp that has a fairly high input bias current that pulls the inverting input high causing the output to be grounded until the light is very bright on the photodiode.

The datasheets show you which pin is which and has all the spec's about bias currents.
 

Alec_t

Jul 7, 2015
3,587
Joined
Jul 7, 2015
Messages
3,587
This will tell you all. Whenever you propose to use an unfamiliar component, always check its datasheet.
 

DalSegno

Jan 14, 2018
2
Joined
Jan 14, 2018
Messages
2
Thank you for your answer guys. But im not really knowledgable on electronics. What alternative should I use?
 

Audioguru

Sep 24, 2016
3,656
Joined
Sep 24, 2016
Messages
3,656
No, most of those opmps will not work in this circuit since their inputs do nothing if they are within a few volts from the negative supply voltage, requiring re-biasing or an additional negative supply. Also, the first opamps listed, the TL07x and TL08x have a problem called "Opamp Input Phase Inversion" which causes the output to suddenly go as high as it can if an input voltage comes within a few volts from the negative supply. But in this circuit the inputs are always at the negative supply voltage. Search for Cmos Rail-to-Rail Opamp instead.
 

Alec_t

Jul 7, 2015
3,587
Joined
Jul 7, 2015
Messages
3,587
My bad. Here are some CMOS op-amps. If Audioguru has a particular favourite perhaps he'd post details?
 
Top