# Current limiter for TIA, realizing dc current source

• Kakeh
In summary, the problem is to limit the current from a photo diode to 5mA while covering a wide dynamic range. The approach followed was to search for a similar solution in a patent, which utilizes current sources and a schottky bridge. There is uncertainty about whether this circuit can handle pulsating current, but initial results were promising. The design problem is how to select the appropriate schottky diode and pJFET for optimal response, as well as how to create stable DC current sources. The suggestion was to search for transistor current sinks and to clarify if a current source or current limit is needed.
Kakeh
Problem:

my photo diode receives pulses of width 10ns-150ns and repeating at rate of 1Hz-50KHz

the current from photo diode depending on incident light can go from 10nA-100mA, so i have two photo diodes to cover the dynamic range, what i want to do is limit the current from a photo diode to 5mA let's say in one channel

Approach Followed:

in search i found some thing similar to my need here

the patent claims: in the picture the current sources 30 and 38 are the maximum current at which the TIA saturates, as soon as the TIA saturates, the schottky bridge isolates the TIA from source,

i have less idea whether the patent circuit can work for pulsating current, but when i tried the results were nice

Design Problem:

how to select the schottky diode and also the pJFET for much better response

if you see schematic i have given a trail of pJFET of all available with LTspice, and same with schottky

How to realize 30 and 38 on practical circuit ?, how can i create stable dc current sources ?

Actually now I've read you post again... Are you after a current source/sink or a current limit? They are different.

## 1. How does a current limiter for TIA work?

A current limiter for TIA (Transimpedance Amplifier) works by controlling the amount of current flowing through the TIA circuit. It uses a feedback mechanism to regulate the input voltage and adjust the current accordingly, thereby limiting the maximum current that can pass through the TIA.

## 2. What is the purpose of a current limiter in a TIA?

The purpose of a current limiter in a TIA is to protect the circuit from damage due to excessive current. It also helps in stabilizing the output voltage and improving the linearity of the TIA.

## 3. How is a dc current source realized in a TIA?

A dc current source in a TIA is realized by using an operational amplifier (op-amp) in the feedback loop of the TIA circuit. The op-amp works as a voltage-controlled current source, providing a stable and constant current to the TIA.

## 4. What are the benefits of using a current limiter in a TIA?

Using a current limiter in a TIA has several benefits, including protecting the circuit from damage, improving stability and linearity, and reducing noise and distortion in the output signal. It also allows for better control and optimization of the current flowing through the TIA.

## 5. Are there any limitations to using a current limiter in a TIA?

While a current limiter can provide several benefits, there are also some limitations to consider. For example, it may introduce additional noise and offset in the TIA circuit, and it may limit the maximum current that can be measured. It is important to carefully design and optimize the current limiter for the specific application to minimize these limitations.

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