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

## Targets

* First Stage: PD-Driver without integrator/Low-Pass-Filter
* 
* 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



* Cfb = 0.1u
* Rfb = 200k ohm

### Without PD reverse bias

* 5us
* 1us

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

* 5us
* 1us
* 500ns (also recut fiber)
* 250ns (also recut fiber)

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

* 250ns (also recut fiber)
* 150ns (also recut fiber)
* 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
* LTC6268-10, 300NTD

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

* 20MHz filter of osc.
* OPA356, <30NTD
* LTC6268-10, 300NTD

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






* 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)
* 
* 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`