---
# System prepended metadata

title: 'Testing report PD-Driver: OPA356-PRE-AMP'
tags: [TestReport, DeWei]

---

# Testing report PD-Driver: OPA356-PRE-AMP

## Targets

* First Stage: PD-Driver without integrator/Low-Pass-Filter
  * ![](https://i.imgur.com/pMdCsr6.png)
* Without PD reverse bias 
  * OPA V+ = 0.22V
    * OPA Vs-: GND
  * OPA V+ = GND
    * OPA Vs-: -0.2V (schottky)
* With PD reverse bias (-2.5V LDO)
  * OPA V+ = 0.22V
    * OPA Vs-: GND
  * OPA V+ = GND
    * OPA Vs-: -0.2V (schottky)

## Test Report

![](https://i.imgur.com/9i9uCRb.png)

![](https://i.imgur.com/8ODOnqk.png)

* Cfb = 0.1u
* Rfb = 200k ohm

### Without PD reverse bias 

* 5us
![](https://i.imgur.com/4MotBmM.png)
* 1us
![](https://i.imgur.com/Ijx1LW4.png)

### With PD reverse bias (-2.5V LDO)

* 5us
![](https://i.imgur.com/8LsmqSf.png)
* 1us
![](https://i.imgur.com/AVaRatg.png)
* 500ns (also recut fiber)
![](https://i.imgur.com/gkLzm8F.png)
* 250ns (also recut fiber)
![](https://i.imgur.com/0Z5a1GE.png)

### With PD reverse bias (-2.5V LDO) and 0.22V bias \@Vin+ of OP-AMP

* 250ns (also recut fiber)
![](https://i.imgur.com/KUDrgTe.png)
* 150ns (also recut fiber)
![](https://i.imgur.com/tYz9iAw.png)
* Because Vin -> Vee(GND) where is not linear anymore

### 100k-With PD reverse bias (-2.5V LDO) and 0.22V bias \@Vin+ of OP-AMP

* 20MHz filter of osc.
* OPA356, <30NTD
![](https://i.imgur.com/gbIM6X4.png)
* LTC6268-10, 300NTD
![](https://i.imgur.com/YWo0If7.png)


### 200k-With PD reverse bias (-2.5V LDO) and 0.22V bias \@Vin+ of OP-AMP

* 20MHz filter of osc.
* OPA356, <30NTD
![](https://i.imgur.com/vrPH4SZ.png)
* LTC6268-10, 300NTD
![](https://i.imgur.com/ziGNhaj.png)


### PCB cleaner(liquet) would damage plastic packaged photodiode

![](https://i.imgur.com/VJoLELa.png)

![](https://i.imgur.com/1dAuIZM.png)

![](https://i.imgur.com/VgawHus.png)

![](https://i.imgur.com/qcV1sau.png)

![](https://i.imgur.com/dhtMg0Q.png)

* Solution: Cleaning PCB with Isopropanol or Alcohol

## Summery

* **We decide to adopt (in the first stage)**
  * OPA356
    * Making completed footprint for 6 pin OP-AMPs?
  * 2.5V reverse bias for photodiode
  * +0.2V ~ +0.1V bias \@ Vin+ of OPA356
  * Power Supplied
    * 5Vcc DC for Vs+ of OPA356
    * GND for Vs- of OPA356
    * Make sure VccIn > 5.15V, otherwise LDO would not work  well
      * Why don't adopt 4.5Vs, see [here](https://hackmd.io/@pd-driver-ntuhep/SJ-VGgJJn)
  * ![](https://i.imgur.com/BsPSzOs.png)
  * This circuit from [datasheet of OPA356](https://www.ti.com/lit/gpn/opa356-q1)
* Be care of the PCB cleaner(liquet)

## Next

* Design integrator
* 4G BW OP-AMP
  * Maybe lock fiber or cut fiber can not be very accurate?

###### tags: `TestReport` `DeWei`