# Issue: \<Solved\> High Rfb of IV Converter

## Background


* If the light source is not very bright, *R1* should be rised
* For our previous result of experiment(1 OPA IVCvT)
* R1 = 500k
* Vo = 3.3V
* ~200 Lux (Estimated by [BPW21R Datasheet](https://www.vishay.com/docs/81519/bpw21r.pdf))
* 

## Problem

* [Resistor has max value on PCB](https://electronics.stackexchange.com/questions/180580/what-is-the-resistance-of-a-typical-pcb)
* > If you're using a 10M resistor and want to maintain 0.1% tolerance (e.g. for a DMM input divider) that means that the board resistance certainly can't be less than 10G ohms.
* > If you really need high impedance for fA measurements, PTFE standoffs or air connections are better than FR4.

* [4kT Noise](https://electronics.stackexchange.com/questions/563136/trouble-to-understand-johnson-nyquist-noise-why-i-dont-find-the-4-in-the-vol)
## Possiable solution

* [Replace PN-PD with PIN-PD](https://www.teamwavelength.com/download/applicationtechnotes/an-ld17.pdf)
* 
* [Intrusment AMP to implement High Gain (3 OPAs)](https://doi.org/10.1364/OE.27.002125)
* Problem: OPA matched
* [T-Tree](https://electronics.stackexchange.com/questions/333055/op-amp-with-t-network-in-the-feedback-path)
###### tags: `issue` `DeWei` `HW-Circiut`