Post Go back to editing

Photodiode Wizard and the SPICE model it generates give very different noise levels

I realize the photodiode wizard is approximate while SPICE is a little more rigorous, but the difference for this circuit is very large:

A low level of noise is estimated:

If I download the spice file for that circuit and run it in ltspice, then integrate noise over the target bandwidth, I get:

SPICE predicts 3x worse noise, and furthermore, SPICE is assuming a brickwall filter at 30 MHz, so real performance would be worse.  Am I doing something wrong in SPICE or is the photodiode wizard just really inaccurate?

Parents
  • Hi mgiacomelli, 

    I am looking into this. Could you send me the design files you generated from the Photodiode Wizard? I would like to see the parameters of your circuit. 

    Thanks, 

    Kris

  • Unfortunately the wizard deleted my design before I could save it, but I was able to type them back in from the SPICE file:

    {
    	"Name": "for forums",
    	"Description": "ddd",
    	"Tool": "PD",
    	"Design": {
    		"photodiode": {
    			"sensor": "",
    			"reverseVoltage": "50",
    			"biasPreference": "positive",
    			"capacitance": "3.5e-10",
    			"shuntResistance": 1000000000,
    			"peakCurrent": "0.001",
    			"peakVoltage": "1",
    			"speedPreference": "bandwidth",
    			"speed": "30000000",
    			"peaking": 0.707107,
    			"stages": "1",
    			"opAmps": [
    				{
    					"stage": "stage_1",
    					"opAmp": "ADA4895-1",
    					"locked": false,
    					"found": true,
    					"valid": true
    				}
    			]
    		}
    	},
    	"CreatedDate": "2018-09-04 05:04:55 PM",
    	"UpdatedDate": "2018-09-04 05:04:55 PM"
    }

Reply
  • Unfortunately the wizard deleted my design before I could save it, but I was able to type them back in from the SPICE file:

    {
    	"Name": "for forums",
    	"Description": "ddd",
    	"Tool": "PD",
    	"Design": {
    		"photodiode": {
    			"sensor": "",
    			"reverseVoltage": "50",
    			"biasPreference": "positive",
    			"capacitance": "3.5e-10",
    			"shuntResistance": 1000000000,
    			"peakCurrent": "0.001",
    			"peakVoltage": "1",
    			"speedPreference": "bandwidth",
    			"speed": "30000000",
    			"peaking": 0.707107,
    			"stages": "1",
    			"opAmps": [
    				{
    					"stage": "stage_1",
    					"opAmp": "ADA4895-1",
    					"locked": false,
    					"found": true,
    					"valid": true
    				}
    			]
    		}
    	},
    	"CreatedDate": "2018-09-04 05:04:55 PM",
    	"UpdatedDate": "2018-09-04 05:04:55 PM"
    }

Children
No Data