Documentation sections

Photodiode Transimpedance Amplifier

POSThttps://rftools.io/api/py/v1/calculate

Slug photodiode-transimpedance. Calculate TIA output voltage, bandwidth, and noise for photodiode circuits. Design transimpedance amplifier gain and feedback components.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of photodiode-transimpedance
Name	Unit	Range	Default	Description
photocurrentnumber	μA	at least 0.001	10	At operating light level
feedbackResistancenumber	kΩ	0.001 … 10000000	100	Feedback Resistor (Rf)
feedbackCapacitancenumber	pF	0.001 … 100000	10	Stabilizing capacitor in parallel with Rf
eSeriesnumber	none	0 … 96	0	Rounds every part to the nearest value in the series; the response and the export are the rounded design's.One of: 0 Ideal values · 12 E12 (10%) · 24 E24 (5%) · 48 E48 (2%) · 96 E96 (1%)

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of photodiode-transimpedance
Field	Unit	Description
outputVoltageVheadline	mV	Output Voltage
bandwidth	kHz	Bandwidth (−3 dB)
noiseVoltage	nV/√Hz	Johnson Noise

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "photodiode-transimpedance",
    "inputs": {
      "photocurrent": 10,
      "feedbackResistance": 100,
      "feedbackCapacitance": 10,
      "eSeries": 0
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("photodiode-transimpedance", {
    "photocurrent": 10,
    "feedbackResistance": 100,
    "feedbackCapacitance": 10,
    "eSeries": 0,
})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "photodiode-transimpedance",
    "inputs": {
      "photocurrent": 10,
      "feedbackResistance": 100,
      "feedbackCapacitance": 10,
      "eSeries": 0
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "photodiode-transimpedance",
	  "inputs": {
	    "photocurrent": 10,
	    "feedbackResistance": 100,
	    "feedbackCapacitance": 10,
	    "eSeries": 0
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "photodiode-transimpedance",
  "values": {
    "outputVoltageV": 999.9999999999999,
    "bandwidth": 159.15494309189535,
    "noiseVoltage": 40.22587013353471
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:photodiode-transimpedance",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "photocurrent": {
          "min": 0.001,
          "max": null,
          "unit": "μA"
        },
        "feedbackResistance": {
          "min": 0.001,
          "max": 10000000,
          "unit": "kΩ"
        },
        "feedbackCapacitance": {
          "min": 0.001,
          "max": 100000,
          "unit": "pF"
        },
        "eSeries": {
          "min": 0,
          "max": 96,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "photocurrent": 10,
      "feedbackResistance": 100,
      "feedbackCapacitance": 10,
      "eSeries": 0
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "photocurrent"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pagePhotodiode Transimpedance Amplifier, at these values