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title = "Transimpedance Amplifiers"
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author = ["Dehaeze Thomas"]
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draft = false
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category = "equipment"
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+++
Tags
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: [Electronics ]({{< relref "electronics.md" >}} )
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## Description {#description}
A transimpedance amplifier is a "current to voltage converter" and is also named a current controlled voltage source.
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It is generally used to interface a sensor which outputs a current proportional to the measurement parameter ([Quadrant Photodiodes]({{< relref " quadrant_photodiodes . md " > }}) for instance).
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## Basic Circuit {#basic-circuit}
A basic transimpedance amplifier circuit is shown in Figure [1 ](#figure--fig:transimpedance-amplifier-schematic ).
It produces an output voltage \\(V\_{\text{out}}\\) proportional to the input current \\(I\_{\text{sig}}\\):
\begin{equation}
\boxed{V\_{\text{out}} = -I\_{\text{sig}} R\_f}
\end{equation}
The gain of the amplifier is simply \\(-R\_f\\) in [V/A].
The feedback resistor creates a Johnson noise that corresponds to a current noise:
\begin{equation}
i\_{n} = \sqrt{4kT/R\_f} \quad [A/\sqrt{Hz}]
\end{equation}
This is usually larger than the amplifier input current noise.
< a id = "figure--fig:transimpedance-amplifier-schematic" > < / a >
{{< figure src = "/ox-hugo/transimpedance_amplifier_schematic.png" caption = "<span class= \"figure-number \">Figure 1: </span>Transimpedance Amplifier; Current in, Voltage out" > }}
More information about transimpedance can be found in [The art of electronics - third edition ]({{< relref "horowitz15_art_of_elect_third_edition.md" >}} ), chapter 8.11.4, especially on the trade-off between gain, noise and bandwidth.
See [this ](https://www.hardware-x.com/article/S2468-0672(21 )00062-6/fulltext) open hardware design.
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## Manufacturers {#manufacturers}
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| Manufacturers | Country |
|------------------------------------------------------------------------------------------------------------|---------|
| [Kistler ](https://www.kistler.com/fr/produits/composants/conditionnement-de-signal/ ) | Swiss |
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| [MMF ](https://www.mmf.de/signal_conditioners.htm ) | Germany |
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| [Femto ](https://www.femto.de/en/products/current-amplifiers.html ) | Germany |
| [FMB Oxford ](https://www.fmb-oxford.com/products/controls-2/control-modules/i404-quad-current-integrator/ ) | UK |
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| [Thorlabs ](https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=7083 ) | UK |
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| [Koheron ](https://www.koheron.com/photonics/pd4q-4-quadrant-photodetector ) | France |
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| [SRS ](https://www.thinksrs.com/products/sr570.html ) | |
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## Bibliography {#bibliography}
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< / div >
